Azure Redis Cache - Impact of high number of cache miss

Question

Hello,

Interested to know about the impact on the Redis Cache server itself when there are a huge number of Cache Misses captured/recorded.

Based on my understanding, Cache Miss means my application doesn't get the data from Redis Cache, and it has to fetch it from different data sources. So ideally, having more number of Cache Miss recorded at the Redis Cache shouldn't have any negative impact on the Cache itself, right?

Thanks in advance.

Answer 1

@Alex
Thank you for the question and for using Microsoft Q&A platform.

You are correct that a cache miss occurs when the requested data is not found in the cache and has to be fetched from a different data source. In general, having a high number of cache misses does not have a negative impact on the Redis Cache server itself. However, it can impact the performance of your application if it has to frequently fetch data from other sources.

1. Frequent cache misses mean more requests are sent to your backend data sources, which can increase their load and potentially slow down your application.
2. Although cache misses don't directly affect Redis, the process of handling these misses can contribute to the server's overall load. If the Redis server is already under high load, this additional processing can exacerbate performance issues.
3. If your application frequently checks the cache and encounters misses, it can still generate a high volume of requests to the Redis server. This can lead to increased CPU and memory usage on the Redis server.
4. Each cache miss results in additional network calls to fetch data from the backend, which can increase latency and affect the user experience.
5. If the cache is near its maximum capacity and items are being evicted frequently, this can lead to memory fragmentation and increased memory pressure on the Redis server.

To mitigate these impacts, you can consider increasing the cache size, optimizing your cache eviction policies, or improving your data access patterns to reduce the frequency of cache misses.

For more information, you can refer to the below documents:
https://redis.io/glossary/cache-miss/
https://learn.microsoft.com/en-us/azure/azure-cache-for-redis/cache-troubleshoot-server
https://learn.microsoft.com/en-us/azure/azure-cache-for-redis/monitor-cache-reference
https://redis.io/blog/cache-eviction-strategies/

Hope this helps. Do let us know if you have any further queries.

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