Caching your REST API
The goal of caching is never having to generate the same response twice. The benefit of doing this is that we gain speed and reduce server load. The best way to cache your API is to put a gateway cache (or reverse proxy) in front of it. Some frameworks provide their own reverse proxies, but a very powerful, open-source one is Varnish.
When a safe method is used on a resource URL, the reverse proxy should cache the response that is returned from your API. It will then use this cached response to answers all subsequent requests for the same resource before they hit your API. When an unsafe method is used on a resource URL, the cache ignores it and passes it to the API. The API is responsible for making sure that the cached resource is invalidated.
HTTP has an unofficial PURGE method that is used for purging caches. When an API receives a call with an unsafe method on a resource, it should fire a PURGE request on that resource so that the reverse proxy knows that the cached resource should be expired. Note that you will still have to configure your reverse proxy to actually remove a resource when it receives a request with the PURGE method.
The result will look like this:
GET /article/1234 HTTP/1.1
- The resource is not cached yet
- Send request to the API
- Store response in cache and return
GET /article/1234 HTTP/1.1
- The resource is cached
- Return response from cache
PUT /article/1234 HTTP/1.1
- Unsafe method, send to API
PURGE /article/1234 HTTP/1.1
- API sends PURGE method to the cache
- The resources is removed from the cache
GET /article/1234 HTTP/1.1
- The resource is not cached yet
- Send request to the API
- Store response in cache and return