Baseline OpenAI end-to-end chat reference architecture

Enterprise chat applications can empower employees through conversational interaction. This is especially true due to the continuous advancement of language models, such as OpenAI's GPT models and Meta's LLaMA models. These chat applications consist of a chat user interface (UI), data repositories that contain domain-specific information pertinent to the user's queries, language models that reason over the domain-specific data to produce a relevant response, and an orchestrator that oversees the interaction between these components.

This article provides a baseline architecture for building and deploying enterprise chat applications that use Azure OpenAI Service language models. The architecture employs prompt flow to create executable flows. These executable flows orchestrate the workflow from incoming prompts out to data stores to fetch grounding data for the language models, along with other required Python logic. The executable flow is deployed to a managed online endpoint with managed compute.

The hosting of the custom chat user interface (UI) follows the baseline app services web application guidance for deploying a secure, zone-redundant, and highly available web application on Azure App Service. In that architecture, App Service communicates to the Azure platform as a service (PaaS) solution through virtual network integration over private endpoints. The chat UI App Service communicates with the managed online endpoint for the flow over a private endpoint. Public access to Azure AI Studio is disabled.

The Azure AI Studio hub is configured with managed virtual network isolation that requires all outbound connections to be approved. With this configuration, a managed virtual network is created, along with managed private endpoints that enable connectivity to private resources, such as the workplace Azure Storage, Azure Container Registry, and Azure OpenAI. These private connections are used during flow authoring and testing, and by flows that are deployed to Machine Learning compute.

A hub is the top-level Azure AI Studio resource which provides a central way to govern security, connectivity, and other concerns across multiple projects. This architecture requires only one project for its workload. If you have additional experiences that require different prompt flows with different logic, potentially using different back-end resources such as data stores, you might consider implementing those in a different project.

Architecture

Download a Visio file of this architecture.

Components

Many components of this architecture are the same as the basic Azure OpenAI end-to-end chat architecture. The following list highlights only the changes to the basic architecture.

• Azure OpenAI is used in both the basic and this baseline architecture. Azure OpenAI is a fully managed service that provides REST API access to Azure OpenAI's language models, including the GPT-4, GPT-3.5-Turbo, and embeddings set of models. The baseline architecture takes advantage of enterprise features such as virtual network and private link that the basic architecture doesn't implement.
• Azure AI Studio is a platform that you can use to build, test, and deploy AI solutions. AI Studio is used in this architecture to build, test, and deploy the prompt flow orchestration logic for the chat application. In this architecture, Azure AI Studio provides the managed virtual network for network security. For more information, see the networking section for more details.
• Application Gateway is a layer 7 (HTTP/S) load balancer and web traffic router. It uses URL path-based routing to distribute incoming traffic across availability zones and offloads encryption to improve application performance.
• Web Application Firewall (WAF) is a cloud-native service that protects web apps from common exploits such as SQL injection and cross-site scripting. Web Application Firewall provides visibility into the traffic to and from your web application, enabling you to monitor and secure your application.
• Azure Key Vault is a service that securely stores and manages secrets, encryption keys, and certificates. It centralizes the management of sensitive information.
• Azure virtual network is a service that enables you to create isolated and secure private virtual networks in Azure. For a web application on App Service, you need a virtual network subnet to use private endpoints for network-secure communication between resources.
• Private Link makes it possible for clients to access Azure platform as a service (PaaS) services directly from private virtual networks without using public IP addressing.
• Azure DNS is a hosting service for DNS domains that provides name resolution using Microsoft Azure infrastructure. Private DNS zones provide a way to map a service's fully qualified domain name (FQDN) to a private endpoint's IP address.

Alternatives

This architecture has multiple components that could be served by other Azure services that might align better to your functional and nonfunctional requirements of your workload. Here are a few such alternatives to be aware of.

Azure Machine Learning workspaces (and portal experiences)

This architecture uses Azure AI Studio to build, test, and deploy prompt flows. Alternatively, you could use Azure Machine Learning workspaces, as both services have overlapping features. While AI Studio is a good choice if you're designing a prompt flow solution, there are some features that Azure Machine Learning currently has better support for. For more information, see the feature comparison. We recommend that you don't mix and match Azure AI Studio and Azure Machine Learning. If your work can be done completely in AI studio, use AI studio. If you still need features from Azure Machine Learning studio, continue to use Azure Machine Learning studio.

Application tier components

There are several managed application services offerings available in Azure that can serve as an application tier for chat UI front end. See Choose an Azure compute service for all compute and Choose an Azure container service for container solutions. For example, while Azure Web Apps and Web App for Containers was selected for both the Chat UI API and the Prompt flow host respectively, similar results could be achieved with Azure Kubernetes Service (AKS) or Azure Container Apps. Choose your workload's application platform based on the workload's specific functional and nonfunctional requirements.

Prompt flow hosting

Deploying prompt flows isn't limited to Machine Learning compute clusters, and this architecture illustrates that with an alternative in Azure App Service. Flows are ultimately a containerized application can be deployed to any Azure service that's compatible with containers. These options include services like Azure Kubernetes Service (AKS), Azure Container Apps, and Azure App Service. Choose an Azure container service based on your orchestration layer's requirements.

An example of why hosting prompt flow hosting on an alternative compute is a consideration is discussed later in this article.

Grounding data store

While this architecture leads with Azure AI Search, your choice of data store for your grounding data is an architectural decision specific to your workload. Many workloads are in fact polyglot and have disparate sources and technologies for grounding data. These data platforms range from existing OLTP data stores, cloud native databases such as Azure Cosmos DB, through specialized solutions such as Azure AI Search. A common, but not required, characteristic for such a data store is vector search. See Choose an Azure service for vector search to explore options in this space.

Considerations and recommendations

Reliability

Reliability ensures your application can meet the commitments you make to your customers. For more information, see Design review checklist for Reliability.

The baseline App Service web application architecture focuses on zonal redundancy for key regional services. Availability zones are physically separate locations within a region. They provide redundancy within a region for supporting services when two or more instances are deployed in across them. When one zone experiences downtime, the other zones within the region might still be unaffected. The architecture also ensures enough instances of Azure services and configuration of those services to be spread across availability zones. For more information, see the baseline to review that guidance.

This section addresses reliability from the perspective of the components in this architecture not addressed in the App Service baseline, including Machine Learning, Azure OpenAI, and AI Search.

Zonal redundancy for flow deployments

Enterprise deployments usually require zonal redundancy. To achieve zonal redundancy in Azure, resources must support availability zones and you must deploy at least three instances of the resource or enable the platform support when instance control isn't available. Currently, Machine Learning compute doesn't offer support for availability zones. To mitigate the potential impact of a datacenter-level catastrophe on Machine Learning components, it's necessary to establish clusters in various regions along with deploying a load balancer to distribute calls among these clusters. You can use health checks to help ensure that calls are only routed to clusters that are functioning properly.

There are some alternatives to Machine Learning compute clusters such as Azure Kubernetes Service (AKS), Azure Functions, Azure Container Apps, and Azure App Service. Each of those services supports availability zones. To achieve zonal redundancy for prompt flow execution, without the added complexity of a multi-region deployment, you should deploy your flows to one of those services.

The following diagram shows an alternate architecture where prompt flows are deployed to App Service. App Service is used in this architecture because the workload already uses it for the chat UI and wouldn't benefit from introducing a new technology into the workload. Workload teams who have experience with AKS should consider deploying in that environment, especially if AKS is being used for other components in the workload.

The diagram is numbered for notable areas in this architecture:

1. Flows are still authored in prompt flow and the network architecture is unchanged. Flow authors still connect to the authoring experience in the AI Studio project through a private endpoint, and the managed private endpoints are used to connect to Azure services when testing flows.

2. This dotted line indicates that containerized executable flows are pushed to Container Registry. Not shown in the diagram are the pipelines that containerize the flows and push to Container Registry. The compute in which those pipelines run must have network line of sight to resources such as the Azure container registry and the AI Studio project.

3. There's another web app deployed to the same app service plan that's already hosting the chat UI. The new web app hosts the containerized prompt flow, colocated on the same app service plan that already runs at a minimum of three instances, spread across availability zones. These App Service instances connect to Container Registry over a private endpoint when loading the prompt flow container image.

4. The prompt flow container needs to connect to all dependent services for flow execution. In this architecture, the prompt flow container connects to AI Search and Azure OpenAI. PaaS services that were exposed only to the Machine Learning managed private endpoint subnet now also need to be exposed in the virtual network so that line of sight can be established from App Service.

Azure OpenAI - reliability

Azure OpenAI doesn't currently support availability zones. To mitigate the potential impact of a datacenter-level catastrophe on model deployments in Azure OpenAI, it's necessary to deploy Azure OpenAI to various regions along with deploying a load balancer to distribute calls among the regions. You can use health checks to help ensure that calls are only routed to clusters that are functioning properly.

To support multiple instances effectively, we recommend that you externalize fine-tuning files, such as to a geo-redundant Storage account. This approach minimizes the state that's stored in the Azure OpenAI for each region. You must still fine tune files for each instance to host the model deployment.

It's important to monitor the required throughput in terms of tokens per minute (TPM) and requests per minute (RPM). Ensure that sufficient TPM assigned from your quota to meet the demand for your deployments and prevent calls to your deployed models from being throttled. A gateway such as Azure API Management can be deployed in front of your Azure OpenAI service or services and can be configured for retry if there are transient errors and throttling. API Management can also be used as a circuit breaker to prevent the service from getting overwhelmed with call, exceeding its quota. To learn more about adding a gateway for reliability concerns, see Access Azure OpenAI and other language models through a gateway.

AI Search - reliability

Deploy AI Search with the Standard pricing tier or higher in a region that supports availability zones, and deploy three or more replicas. The replicas automatically spread evenly across availability zones.

Consider the following guidance for determining the appropriate number of replicas and partitions:

• Monitor AI Search.

• Use monitoring metrics and logs and performance analysis to determine the appropriate number of replicas to avoid query-based throttling and partitions and to avoid index-based throttling.

Azure AI Studio - reliability

If you deploy to compute clusters behind the Machine Learning managed online endpoint, consider the following guidance regarding scaling:

• Automatically scale your online endpoints to ensure enough capacity is available to meet demand. If usage signals aren't timely enough due to burst usage, consider overprovisioning to prevent an impact on reliability from too few instances being available.

• Consider creating scaling rules based on deployment metrics such as CPU load and endpoint metrics such as request latency.

• No less than three instances should be deployed for an active production deployment.

• Avoid deployments against in-use instances. Instead deploy to a new deployment and shift traffic over after the deployment is ready to receive traffic.

Managed online endpoints act as a load balancer and router for the managed compute running behind them. You're able to configure the percentage of traffic that should be routed to each deployment, as long as the percentages add up to 100%. You're also able to deploy a managed online endpoint with 0% traffic being routed to any deployment. If, like in the provided reference implementation, you're using infrastructure as code (IaC) to deploy your resources, including your managed online endpoints, there's a reliability concern. If you have traffic configured to route to deployments (created via CLI or the Azure AI Studio) and you perform a subsequent IaC deployment that includes the managed online endpoint, even if it doesn't update the managed online endpoint in any way, the endpoint traffic reverts to routing 0% traffic. Effectively, this means that your deployed prompt flows will no longer be reachable until you adjust the traffic back to where you want it.

Multi-region design

This architecture isn't built to be a regional stamp in a multi-region architecture. It does provide high availability within a single region due to its complete usage of availability zones, but lacks some key components to make this truly ready for a multi-region solution. These are some components or considerations that are missing from this architecture:

• Global ingress and routing
• DNS management strategy
• Data replication (or isolation) strategy
• An active-active, active-passive, or active-cold designation
• A failover and failback strategy to achieve your workload's RTO and RPO
• Decisions around region availability for developer experiences in the Azure Studio Hub resource

If your workload's requirements require a multi-region strategy, you need to invest in additional design efforts around components and operational processes on top of what is presented in this architecture. You design to support load balancing or failover at the following layers:

• Grounding data
• Model hosting
• Orchestration layer (Prompt flow in this architecture)
• Client-facing UI

In addition, you'll need maintain business continuity in observability, portal experiences, and responsible AI concerns like content safety.

Security

Security provides assurances against deliberate attacks and the abuse of your valuable data and systems. For more information, see Design review checklist for Security.

This architecture extends the security footprint implemented in the Basic end-to-end chat with Azure OpenAI architecture. While the basic architecture uses system-assigned managed identities and system-assigned role assignments, this architecture uses user-assigned identities with manually created role assignments.

The architecture implements a network security perimeter, along with the identity perimeter implemented in the basic architecture. From a network perspective, the only thing that should be accessible from the internet is the chat UI via Application Gateway. From an identity perspective, the chat UI should authenticate and authorize requests. Managed identities are used, where possible, to authenticate applications to Azure services.

Along with networking considerations, this section describes security considerations for key rotation and Azure OpenAI model fine tuning.

Identity and access management

When using user-assigned managed identities, consider the following guidance:

• Create separate managed identities for the following Azure AI Studio and Machine Learning resources, where applicable:
  • AI Studio Hub
  • AI Studio projects for flow authoring and management
  • Online endpoints in the deployed flow if the flow is deployed to a managed online endpoint
• Implement identity-access controls for the chat UI by using Microsoft Entra ID

Create separate projects and online endpoints for different prompt flows that you want to isolate from others from a permissions perspective. Create a separate managed identity for each project and managed online endpoint. Give prompt flow authors access to only the projects they require.

When you onboard users to Azure AI Studio projects to perform functions like authoring flows, you need to make least privilege role assignments the resources they require.

Machine Learning role-based access roles

Like in the basic architecture, the system automatically creates role assignments for the system-assigned managed identities. Because the system doesn't know what features of the hub and projects you may use, it creates role assignments support all of the potential features. The automatically created role assignments might over provision privileges based on your use case. An example is the 'Contributor' role assigned to the hub for the container registry, where it only likely requires 'Reader' access to the control plane. If you need to limit permissions further for least privilege goals, you must use user-assigned identities. You'll create and maintain these role assignments yourself.

Because of the maintenance burden of managing all the required assignments, this architecture favors operational excellence over absolute least privilege role assignments. Note that you have to make all the assignments listed in the table.

Managed identity	Scope	Role assignments
Hub managed identity	Contributor	Resource Group
Hub managed identity	Hub	Azure AI Administrator
Hub managed identity	Container Registry	Contributor
Hub managed identity	Key Vault	Contributor
Hub managed identity	Key Vault	Administrator
Hub managed identity	Storage Account	Reader
Hub managed identity	Storage Account	Storage Account Contributor
Hub managed identity	Storage Account	Storage Blob Data Contributor
Hub managed identity	Storage Account	Storage File Data Privileged Contributor
Hub managed identity	Storage Account	Storage Table Data Contributor
Project managed identity	Project	Azure AI Administrator
Project managed identity	Container Registry	Contributor
Project managed identity	Key Vault	Contributor
Project managed identity	Key Vault	Administrator
Project managed identity	Storage Account	Reader
Project managed identity	Storage Account	Storage Account Contributor
Project managed identity	Storage Account	Storage Blob Data Contributor
Project managed identity	Storage Account	Storage File Data Privileged Contributor
Project managed identity	Storage Account	Storage Table Data Contributor
Online endpoint managed identity	Project	Azure Machine Learning Workspace Connection Secrets
Online endpoint managed identity	Project	AzureML Metrics Writer
Online endpoint managed identity	Container Registry	ACRPull
Online endpoint managed identity	Azure OpenAI	Cognitive Services OpenAI User
Online endpoint managed identity	Storage Account	Storage Blob Data Contributor
Online endpoint managed identity	Storage Account	Storage Blob Data Reader
App Service (when prompt flow is deployed to App Service)	Azure OpenAI	Cognitive Services OpenAI User
Portal User (prompt flow development)	Azure OpenAI	Cognitive Services OpenAI User
Portal User (prompt flow development)	Storage Account	Storage Blob Data Contributor (use conditional access)
Portal User (prompt flow development)	Storage Account	Storage File Data Privileged Contributor

It's important to understand that the AI Studio hub has Azure resources that are shared across projects, such as a Storage Account and Container Registry. If you have users that only need access to a subset of the projects, consider using role assignment conditions, for Azure services that support them, to provide least privilege access to resources. For example, blobs in Azure Storage support role assignment conditions. For a user that requires access to a subset of the projects, instead of assigning permissions on a per-container basis, use role access conditions to limit permissions to the blob containers used by those projects. Each project has a unique GUID that serves as a prefix for the names of the blob containers used in that project. That GUID can be used as part of the role assignment conditions.

The hub has a requirement to have Contributor access to the hub resource group in order to allow it to create and managed hub and project resources. A side effect of that the hub has control plane access to any resource also in the resource group. Any Azure resources not directly related to the hub and its projects should be created in a separate resource group. We recommend you create, at a minimum, two resource groups for a workload team using a self-managed Azure AI Studio Hub. One resource group to contain the hub, its projects, and all of its direct dependencies like the Azure container registry, Key Vault, and so on. One resource group to contain everything else in your workload.

We recommend that you minimize the use of Azure resources needed for the hub's operation (Container Registry, Storage Account, Key Vault, Application Insights) by other components in your workloads. For example, if you need to store secrets as part of your workload, you should create a separate Key Vault apart from the key vault associated with the hub. The hub Key Vault should only be used by the hub to store hub and project secrets.

Ensure that for each distinct project, the role assignments for its dependencies don't provide access to resources the portal user and managed online endpoint managed identity don't require. For example, the Cognitive Services OpenAI User role assignment to Azure OpenAI grants access to all deployments for that resource. There's no way to restrict flow authors or managed online endpoint managed identities with that role assignment access to specific model deployments in Azure OpenAI. For scenarios such as this, our guidance is to deploy services such as Azure OpenAI and Azure AI Search on a per-project basis and don't deploy resources to those services that flow authors or managed online endpoint managed identities shouldn't have access to. For example, only deploy models to the project Azure OpenAI instance that the project requires access to. Only deploy indexes to the project Azure AI Search instance that the project should have access to.

Networking

Along with identity-based access, network security is at the core of the baseline end-to-end chat architecture that uses OpenAI. From a high level, the network architecture ensures that:

• Only a single, secure entry point for chat UI traffic.
• Network traffic is filtered.
• Data in transit is encrypted end-to-end with Transport Layer Security (TLS).
• Data exfiltration is minimized by using Private Link to keep traffic in Azure.
• Network resources are logically grouped and isolated from each other through network segmentation.

Network flows

Two flows in this diagram are covered in the baseline App Service web application architecture: The inbound flow from the end user to the chat UI (1) and the flow from App Service to Azure PaaS services (2). This section focuses on the Machine Learning online endpoint flow. The following flow goes from the chat UI that runs in the baseline App Service web application to the flow deployed to Machine Learning compute:

1. The call from the App Service-hosted chat UI is routed through a private endpoint to the Machine Learning online endpoint.
2. The online endpoint routes the call to a server running the deployed flow. The online endpoint acts as both a load balancer and a router.
3. Calls to Azure PaaS services required by the deployed flow are routed through managed private endpoints.

Ingress to Machine Learning

In this architecture, public access to the Machine Learning workspace is disabled. Users can access the workspace via private access because the architecture follows the private endpoint for the Machine Learning workspace configuration. In fact, private endpoints are used throughout this architecture to complement identity-based security. For example, your App Service-hosted chat UI can connect to PaaS services that aren't exposed to the public internet, including Machine Learning endpoints.

Private endpoint access is also required for connecting to the Machine Learning workspace for flow authoring.

The diagram shows a prompt flow author connecting through Azure Bastion to a virtual machine jump box. From that jump box, the author can connect to the Machine Learning workspace through a private endpoint in the same network as the jump box. Connectivity to the virtual network could also be accomplished through ExpressRoute or VPN gateways and virtual network peering.

Flow from the Azure AI Studio managed virtual network to Azure PaaS services

We recommend that you configure the Azure AI Studio hub for managed virtual network isolation that requires all outbound connections to be approved. This architecture follows that recommendation. There are two types of approved outbound rules. Required outbound rules are to resources required for the solution to work, such as Container Registry and Storage. User-defined outbound rules are to custom resources, such as Azure OpenAI or AI Search, that your workflow is going to use. You must configure user-defined outbound rules. Required outbound rules are configured when the managed virtual network is created. The managed virtual network is deployed on-demand when you first use it and is persistant from then on.

The outbound rules can be private endpoints, service tags, or fully qualified domain names (FQDNs) for external public endpoints. In this architecture, connectivity to Azure services such as Container Registry, Storage, Azure Key Vault, Azure OpenAI, and AI Search are connected through private link. Although not in this architecture, some common operations that might require configuring an FQDN outbound rule are downloading a pip package, cloning a GitHub repo, or downloading base container images from external repositories.

Virtual network segmentation and security

The network in this architecture has separate subnets for the following purposes:

• Application Gateway

• App Service integration components

• Private endpoints

• Azure Bastion

• Jump box virtual machine

• Training and Scoring subnets - both of these are for bring your own compute related to training and inferencing. In this architecture, we're not doing training and we're using managed compute.

• Scoring

Each subnet has a network security group (NSG) that limits both inbound and outbound traffic for those subnets to just what's required. The following table shows a simplified view of the NSG rules that the baseline adds to each subnet. The table provides the rule name and function.

Subnet	Inbound	Outbound
snet-appGateway	Allowances for our chat UI users source IPs (such as public internet), plus required items for the service.	Access to the App Service private endpoint, plus required items for the service.
snet-PrivateEndpoints	Allow only traffic from the virtual network.	Allow only traffic to the virtual network.
snet-AppService	Allow only traffic from the virtual network.	Allow access to the private endpoints and Azure Monitor.
AzureBastionSubnet	See guidance in Working with NSG access and Azure Bastion.	See guidance in Working with NSG access and Azure Bastion.
snet-jumpbox	Allow inbound Remote Desktop Protocol (RDP) and SSH from the Azure Bastion host subnet.	Allow access to the private endpoints
snet-agents	Allow only traffic from the virtual network.	Allow only traffic to the virtual network.
snet-training	Allow only traffic from the virtual network.	Allow only traffic to the virtual network.
snet-scoring	Allow only traffic from the virtual network.	Allow only traffic to the virtual network.

All other traffic is explicitly denied.

Consider the following points when implementing virtual network segmentation and security.

• Enable DDoS Protection for the virtual network with a subnet that's part of an application gateway with a public IP address.

• Add an NSG to every subnet where possible. Use the strictest rules that enable full solution functionality.

• Use application security groups to group NSGs. Grouping NSGs makes rule creation easier for complex environments.

Key rotation

There's one service in this architecture that uses key-based authentication: the Machine Learning managed online endpoint. Because you use key-based authentication for this service, it's important to:

• Store the key in a secure store, like Key Vault, for on-demand access from authorized clients, such as the Azure Web App hosting the prompt flow container.

• Implement a key rotation strategy. If you manually rotate the keys, create a key expiration policy and use Azure Policy to monitor whether the key was rotated.

OpenAI model fine tuning

If you fine tune OpenAI models in your implementation, consider the following guidance:

• If you upload training data for fine tuning, consider using customer-managed keys for encrypting that data.

• If you store training data in a store such as Azure Blob Storage, consider using a customer-managed key for data encryption, a managed identity to control access to the data, and a private endpoint to connect to the data.

Governance through policy

To help ensure alignment with security, consider using Azure Policy and network policy so that deployments align to the requirements of the workload. The use of platform automation through policy reduces the burden of manual validation steps and ensures governance even if pipelines are bypassed. Consider the following security policies:

• Disable key or other local authentication access in services like Azure AI services and Key Vault.
• Require specific configuration of network access rules or NSGs.
• Require encryption, such as the use of customer-managed keys.

Azure AI Studio role assignments for Azure Key Vault

The Azure AI Studio managed identity requires both control plane (Contributor) and data plane (Key Vault Administrator) role assignments. This means that this identity has read and write access to all secrets, keys, and certificates stored in the Azure key vault. If your workload has services other than Azure AI Studio that require access to secrets, keys, or certificates in Key Vault, your workload or security team may not be comfortable with the Azure AI Studio hub managed identity having access to those artifacts. In this case, consider deploying a Key Vault instance specifically for the Azure AI Studio hub, and other Azure Key Vault instances as appropriate for other parts of your workload.

Cost optimization

Cost optimization is about looking at ways to reduce unnecessary expenses and improve operational efficiencies. For more information, see Design review checklist for Cost Optimization.

To see a pricing example for this scenario, use the Azure pricing calculator. You need to customize the example to match your usage because this example only includes the components included in the architecture. The most expensive components in the scenario are DDoS Protection and the firewall that is deployed as part of the managed online endpoint. Other notable costs are the chat UI and prompt flow compute and AI Search. Optimize those resources to save the most cost.

Compute

Prompt flow supports multiple options to host the executable flows. The options include managed online endpoints in Machine Learning, AKS, App Service, and Azure Kubernetes Service. Each of these options has their own billing model. The choice of compute affects the overall cost of the solution.

Azure OpenAI

Azure OpenAI is a consumption-based service, and as with any consumption-based service, controlling demand against supply is the primary cost control. To do that in Azure OpenAI specifically, you need to use a combination of approaches:

• Control clients. Client requests are the primary source of cost in a consumption model, so controlling client behavior is critical. All clients should:

  • Be approved. Avoid exposing the service in such a way that supports free-for-all access. Limit access both through network and identity controls, such as keys or role-based access control (RBAC).

  • Be self-controlled. Require clients to use the token-limiting constraints offered by the API calls, such as max_tokens and max_completions.

  • Use batching, where practical. Review clients to ensure they're appropriately batching prompts.

  • Optimize prompt input and response length. Longer prompts consume more tokens, raising the cost, yet prompts that are missing sufficient context don't help the models yield good results. Create concise prompts that provide enough context to allow the model to generate a useful response. Likewise, ensure that you optimize the limit of the response length.

• Azure OpenAI playground usage should be as necessary and on preproduction instances, so that those activities aren't incurring production costs.

• Select the right AI model. Model selection also plays a large role in the overall cost of Azure OpenAI. All models have strengths and weaknesses and are individually priced. Use the correct model for the use case to make sure that you're not overspending on a more expensive model when a less expensive model yields acceptable results. In this chat reference implementation, GPT 3.5-turbo was chosen over GPT-4 to save about an order of magnitude of model deployment costs while achieving sufficient results.

• Understand billing breakpoints. Fine-tuning is charged per-hour. To be the most efficient, you want to use as much of that time available per hour to improve the fine-tuning results while avoiding just slipping into the next billing period. Likewise, the cost for 100 images from image generation is the same as the cost for one image. Maximize the price break points to your advantage.

• Understand billing models. Azure OpenAI is also available in a commitment-based billing model through the provisioned throughput offering. After you have predictable usage patterns, consider switching to this prepurchase billing model if it's more cost effective at your usage volume.

• Set provisioning limits. Ensure that all provisioning quota is allocated only to models that are expected to be part of the workload, on a per-model basis. Throughput to already deployed models isn't limited to this provisioned quota while dynamic quota is enabled. Quota doesn't directly map to costs and that cost might vary.

• Monitor pay-as-you-go usage. If you use pay-as-you-go pricing, monitor usage of TPM and RPM. Use that information to inform architectural design decisions such as what models to use, and optimize prompt sizes.

• Monitor provisioned throughput usage. If you use provisioned throughput, monitor provision-managed usage to ensure that you aren't underusing the provisioned throughput that you purchased.

• Cost management. Follow the guidance on using cost management features with OpenAI to monitor costs, set budgets to manage costs, and create alerts to notify stakeholders of risks or anomalies.

Operational excellence

Operational excellence covers the operations processes that deploy an application and keep it running in production. For more information, see Design review checklist for Operational Excellence.

Built-in prompt flow runtimes

Like in the basic architecture, this architecture uses the Automatic Runtime to minimize operational burden. The automatic runtime is a serverless compute option within Machine Learning that simplifies compute management and delegates most of the prompt flow configuration to the running application's requirements.txt file and flow.dag.yaml configuration. This makes this choice low maintenance, ephemeral, and application-driven. Using Compute Instance Runtime or externalized compute, such as in this architecture, requires a more workload team-managed lifecycle of the compute, and should be selected when workload requirements exceed the configuration capabilities of the automatic runtime option.

Monitoring

Like in the basic architecture, diagnostics are configured for all services. All services but App Service are configured to capture all logs. App Service is configured to capture AppServiceHTTPLogs, AppServiceConsoleLogs, AppServiceAppLogs, and AppServicePlatformLogs. In production, all logs are likely excessive. Tune log streams to your operational needs. For this architecture, the Azure Machine Learning logs used by the Azure AI Studio project that are of interest include: AmlComputeClusterEvent, AmlDataSetEvent, AmlEnvironmentEvent, and AmlModelsEvent.

Evaluate building custom alerts for the resources in this architecture such as those found in the Azure Monitor baseline alerts. For example:

• Container Registry alerts
• Machine Learning and Azure OpenAI alerts
• Azure Web Apps alerts

Be sure to track usage of tokens against your Azure OpenAI model deployments. In this architecture, Prompt flow tracks token usage through its integration with Azure Application Insights.

Language model operations

Deployment for Azure OpenAI-based chat solutions like this architecture should follow the guidance in GenAIOps with prompt flow with Azure DevOps and with GitHub. Additionally, it must consider best practices for continuous integration and continuous delivery (CI/CD) and network-secured architectures. The following guidance addresses the implementation of flows and their associated infrastructure based on the GenAIOps recommendations. This deployment guidance doesn't include the front-end application elements, which are unchanged from in the Baseline highly available zone-redundant web application architecture.

Development

Prompt flow offers both a browser-based authoring experience in Azure AI Studio or through a Visual Studio Code extension. Both options store the flow code as files. When you use Azure AI Studio, the files are stored in a Storage account. When you work in Microsoft Visual Studio Code, the files are stored in your local file system.

In order to follow best practices for collaborative development, the source files should be maintained in an online source code repository such as GitHub. This approach facilitates tracking of all code changes, collaboration between flow authors and integration with deployment flows that test and validate all code changes.

For enterprise development, use the Microsoft Visual Studio Code extension and the prompt flow SDK/CLI for development. Prompt flow authors can build and test their flows from Microsoft Visual Studio Code and integrate the locally stored files with the online source control system and pipelines. While the browser-based experience is well suited for exploratory development, with some work, it can be integrated with the source control system. The flow folder can be downloaded from the flow page in the Files panel, unzipped, and pushed to the source control system.

Evaluation

Test the flows used in a chat application just as you test other software artifacts. It's challenging to specify and assert a single "right" answer for language model outputs, but you can use a language model itself to evaluate responses. Consider implementing the following automated evaluations of your language model flows:

• Classification accuracy: Evaluates whether the language model gives a "correct" or "incorrect" score and aggregates the outcomes to produce an accuracy grade.

• Coherence: Evaluates how well the sentences in a model's predicted answer are written and how they coherently connect with each other.

• Fluency: Assesses the model's predicted answer for its grammatical and linguistic accuracy.

• Groundedness against context: Evaluates how well the model's predicted answers are based on preconfigured context. Even if the language model responses are correct, if they can't be validated against the given context, then such responses aren't grounded.

• Relevance: Evaluates how well the model's predicted answers align with the question asked.

Consider the following guidance when implementing automated evaluations:

• Produce scores from evaluations and measure them against a predefined success threshold. Use these scores to report test pass/fail in your pipelines.

• Some of these tests require preconfigured data inputs of questions, context, and ground truth.

• Include enough question-answer pairs to ensure the results of the tests are reliable, with at least 100-150 pairs recommended. These question-answer pairs are referred to as your "golden dataset." A larger population might be required depending on the size and domain of your dataset.

• Avoid using language models to generate any of the data in your golden dataset.

Deployment Flow

1. The prompt engineer/data scientist opens a feature branch where they work on the specific task or feature. The prompt engineer/data scientist iterates on the flow using prompt flow for Microsoft Visual Studio Code, periodically committing changes and pushing those changes to the feature branch.

2. Once local development and experimentation are completed, the prompt engineer/data scientist opens a pull request from the Feature branch to the Main branch. The pull request (PR) triggers a PR pipeline. This pipeline runs fast quality checks that should include:

   • Execution of experimentation flows
   • Execution of configured unit tests
   • Compilation of the codebase
   • Static code analysis

3. The pipeline can contain a step that requires at least one team member to manually approve the PR before merging. The approver can't be the committer and they mush have prompt flow expertise and familiarity with the project requirements. If the PR isn't approved, the merge is blocked. If the PR is approved, or there's no approval step, the feature branch is merged into the Main branch.

4. The merge to Main triggers the build and release process for the Development environment. Specifically:

   1. The CI pipeline is triggered from the merge to Main. The CI pipeline performs all the steps done in the PR pipeline, and the following steps:
   • Experimentation flow
   • Evaluation flow
   • Registers the flows in the Machine Learning Registry when changes are detected
   1. The CD pipeline is triggered after the completion of the CI pipeline. This flow performs the following steps:
   • Deploys the flow from the Machine Learning registry to a Machine Learning online endpoint
   • Runs integration tests that target the online endpoint
   • Runs smoke tests that target the online endpoint

5. An approval process is built into the release promotion process – upon approval, the CI & CD processes described in steps 4.a. & 4.b. are repeated, targeting the Test environment. Steps a. and b. are the same, except that user acceptance tests are run after the smoke tests in the Test environment.

6. The CI & CD processes described in steps 4.a. & 4.b. are run to promote the release to the Production environment after the Test environment is verified and approved.

7. After release into a live environment, the operational tasks of monitoring performance metrics and evaluating the deployed language models take place. This includes but isn't limited to:

   • Detecting data drifts
   • Observing the infrastructure
   • Managing costs
   • Communicating the model's performance to stakeholders

Deployment guidance

You can use Machine Learning endpoints to deploy models in a way that enables flexibility when releasing to production. Consider the following strategies to ensure the best model performance and quality:

• Blue/green deployments: With this strategy, you can safely deploy your new version of the web service to a limited group of users or requests before directing all traffic over to the new deployment.

• A/B testing: Not only are blue/green deployments effective for safely rolling out changes, they can also be used to deploy new behavior that allows a subset of users to evaluate the impact of the change.

• Include linting of Python files that are part of the prompt flow in your pipelines. Linting checks for compliance with style standards, errors, code complexity, unused imports, and variable naming.

• When you deploy your flow to the network-isolated Machine Learning workspace, use a self-hosted agent to deploy artifacts to your Azure resources.

• The Machine Learning model registry should only be updated when there are changes to the model.

• The language models, the flows, and the client UI should be loosely coupled. Updates to the flows and the client UI can and should be able to be made without affecting the model and vice versa.

• When you develop and deploy multiple flows, each flow should have its own lifecycle, which allows for a loosely coupled experience when promoting flows from experimentation to production.

Infrastructure

When you deploy the baseline Azure OpenAI end-to-end chat components, some of the services provisioned are foundational and permanent within the architecture, whereas other components are more ephemeral in nature, their existence tied to a deployment. Also, while the managed virtual network is foundational, it's automatically provisioned when you create a compute instance which leads to some considerations.

Foundational components

Some components in this architecture exist with a lifecycle that extends beyond any individual prompt flow or any model deployment. These resources are typically deployed once as part of the foundational deployment by the workload team, and maintained apart from new, removed, or updates to the prompt flows or model deployments.

• Machine Learning workspace
• Storage account for the Machine Learning workspace
• Container Registry
• AI Search
• Azure OpenAI
• Azure Application Insights
• Azure Bastion
• Azure Virtual Machine for the jump box

Ephemeral components

Some Azure resources are more tightly coupled to the design of specific prompt flows. This approach allows these resources to be bound to the lifecycle of the component and become ephemeral in this architecture. Azure resources are affected when the workload evolves, such as when flows are added or removed or when new models are introduced. These resources get re-created and prior instances removed. Some of these resources are direct Azure resources and some are data plane manifestations within their containing service.

• The model in the Machine Learning model registry should be updated, if changed, as part of the CD pipeline.

• The container image should be updated in the container registry as part of the CD pipeline.

• A Machine Learning endpoint is created when a prompt flow is deployed if the deployment references an endpoint that doesn't exist. That endpoint needs to be updated to turn off public access.

• The Machine Learning endpoint's deployments are updated when a flow is deployed or deleted.

• The key vault for the client UI must be updated with the key to the endpoint when a new endpoint is created.

On-demand managed virtual network

The managed virtual network is automatically provisioned when you first create a compute instance. If you're using infrastructure as code to deploy your hub, and you don't have AI Studio compute resources in the Bicep, the managed virtual network isn't deployed and you'll receive an error when connecting to Azure AI Studio. You'll need to perform a one-time action to manually provision the managed virtual network after your IaC deployment.

Resource organization

If you have a scenario where the hub is centrally owned by a team other than the workload team, you may choose to deploy projects to separate resource groups. If you're using infrastrastructure as code, you can accomplish that by setting a different resource group in the Bicep. If you're using the portal, you can set the defaultWorkspaceResourceGroup property under the workspaceHubConfig to the resource group you would like your projects to be created.

Performance efficiency

Performance efficiency is the ability of your workload to scale to meet the demands placed on it by users in an efficient manner. For more information, see Design review checklist for Performance Efficiency.

This section describes performance efficiency from the perspective of Azure Search, Azure OpenAI, and Machine Learning.

Azure Search - performance efficiency

Follow the guidance to analyze performance in AI Search.

Azure OpenAI - performance efficiency

• Determine whether your application requires provisioned throughput or the shared hosting, or consumption, model. Provisioned throughput ensures reserved processing capacity for your OpenAI model deployments, which provides predictable performance and throughput for your models. This billing model is unlike the shared hosting, or consumption, model. The consumption model is best-effort and might be subject to noisy neighbor or other stressors on the platform.

• Monitor provision-managed utilization for provisioned throughput.

Machine Learning - performance efficiency

If you deploy to Machine Learning online endpoints:

• Follow the guidance about how to autoscale an online endpoint. Do this to remain closely aligned with demand without excessive overprovisioning, especially in low-usage periods.

• Choose the appropriate virtual machine SKU for the online endpoint to meet your performance targets. Test the performance of both lower instance count and bigger SKUs versus larger instance count and smaller SKUs to find an optimal configuration.

Deploy this scenario

To deploy and run the reference implementation, follow the steps in the OpenAI end-to-end baseline reference implementation.

Contributors

This article is maintained by Microsoft. It was originally written by the following contributors.

• Rob Bagby | Patterns & Practices - Microsoft
• Freddy Ayala | Cloud Solution Architect - Microsoft
• Prabal Deb | Senior Software Engineer - Microsoft
• Raouf Aliouat | Software Engineer II - Microsoft
• Ritesh Modi | Principal Software Engineer - Microsoft
• Ryan Pfalz | Senior Solution Architect - Microsoft

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Next step

Related resources

• Azure OpenAI
• Azure OpenAI language models
• Prompt flow in Azure AI Studio
• Workspace managed virtual network isolation
• Configure a private endpoint for a Machine Learning workspace
• Content filtering