Why is the Nginx fastcgi_cache always resulting in MISS?

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There could be several reasons for Nginx fastcgi_cache always resulting in MISS:

1. Cache Key Mismatch: Nginx uses the request URI as a cache key. If the key is not properly formed or if the request contains dynamic parameters, the cache may not be able to find the previously cached content.

2. Cache Purging: If the cache is configured to expire too frequently, or if it is being purged too often, then the cache may not be able to store content long enough to serve requests.

3. Load Balancer: If the application is running behind a load balancer, then the cache key may be unique for each backend server, resulting in a MISS for every request.

4. Cache Bypass: If the request contains cookies or other headers that bypass the cache, then the cache will not be used, resulting in a MISS.

5. Cache Size: If the Nginx fastcgi_cache size is too small, or if there is not enough available disk space, then the cache may not be able to store all the requests, resulting in a MISS for some requests.