FastCGI cache in Nginx - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is FastCGI cache in nginx?

FastCGI cache is a feature in nginx that stores dynamic content generated by FastCGI servers (like PHP-FPM) on disk. This helps serve repeated requests faster by avoiding running the backend script every time.

beginner

Which directive in nginx config enables FastCGI caching?

The directive fastcgi_cache enables FastCGI caching by specifying the cache zone name to use for storing cached responses.

intermediate

What does the fastcgi_cache_path directive do?

It defines the location on disk where cached files are stored, the cache size, and cache key zone name. It sets up the cache storage parameters.

intermediate

How does nginx decide if a cached FastCGI response is valid?

Nginx uses cache control headers like Cache-Control and Expires from the backend response, and directives like fastcgi_cache_valid to determine cache validity duration.

intermediate

What is the purpose of fastcgi_cache_key?

It defines the unique key used to store and retrieve cached content. Usually, it includes the request URI and other variables to differentiate cache entries.

Which directive sets the disk location for FastCGI cache in nginx?

A fastcgi_cache_path

B fastcgi_cache_key

C fastcgi_cache_valid

D fastcgi_cache_use_stale

The fastcgi_cache_path directive defines where cached files are stored on disk.

What does fastcgi_cache_valid 200 10m; mean?

A Cache all responses for 200 minutes

B Cache 200 OK responses for 10 minutes

C Cache only 10 responses with status 200

D Disable caching for 200 status

It tells nginx to cache responses with HTTP status 200 for 10 minutes.

How does nginx serve a cached FastCGI response?

A By reading the cached file from disk and sending it directly

B By running the backend script again

C By redirecting to the backend server

D By clearing the cache first

Nginx serves cached content directly from disk without contacting the backend.

Which directive defines the cache zone name used in fastcgi_cache?

A fastcgi_cache_valid

B fastcgi_cache_key

C fastcgi_cache_path

D fastcgi_cache_methods

The fastcgi_cache_path directive defines the cache zone name used later by fastcgi_cache.

What is the effect of fastcgi_cache_use_stale error timeout?

A Cache only error responses

B Always clear cache on error

C Disable cache on timeout

D Serve stale cache if backend returns error or times out

This directive allows nginx to serve stale cached content if the backend is down or slow.

Explain how to configure FastCGI cache in nginx from scratch.

Think about where to store cache, how to name it, and how to use it in your server block.

Describe how nginx decides when to serve cached FastCGI content versus fetching fresh content.

Consider cache expiration and backend response status.