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Caching

There are some reasons why you have to consider to use Caching

  • improve speed
  • reduce latency
  • reduce server load
  • reduce network traffic

Goal of caching is to never generate the same response twice.

Tip: For security reasons, do not allow sensitive data to be cached. Use server side mechanisms like setting Cache-Control to no-store in the response header. Additionally you should use HTTPS.

Expires HTTP Header

The Expires HTTP header is a basic means of controlling caches - it tells all caches how long the associated representation is fresh for. After that time, caches will always check back with the origin server to see, if a document is changed. Expires headers are supported by practically every cache. Expires headers are especially good for making static images (like navigation bars and buttons) cacheable. Because they don't change much, you can set extremely long expiry time on them, making your site appear much more responsive to your users.

GET /user_management/v1/users/BE14A7269802498F992813885546D058

HTTP/1.1 200 OK
...
Expires: Fri, 30 Oct 2015 14:19:41 GMT
Last-Modified: Mon, 29 Jun 2015 02:28:12 GMT
Content-Type: text/json; charset=utf-8
Content-Length: ...
{ "id": "BE14A7269802498F992813885546D058", "name": "Mustermann" }

You can find more infos in: https://www.mnot.net/cache_docs/#CACHE-CONTROL

Cache-Control Header

Use Cache-Control header that indicates, whether the data in the body of the response can be safely cached by the client or an intermediate server. Use max-age to indicate after how many seconds the response should be considered out-of-date. The following example shows an HTTP GET request and the corresponding response that includes a Cache-Control header:

GET /user_management/v1/users/BE14A7269802498F992813885546D058

HTTP/1.1 200 OK
...
Cache-Control: max-age=600, private
Content-Type: text/json; charset=utf-8
Content-Length: ...
{ "id": "BE14A7269802498F992813885546D058", "name": "Mustermann" }

You can find a detailed explanation of the different Cache-Control opportunities in: https://www.mnot.net/cache_docs/#CACHE-CONTROL

ETag

You can use an ETag (Entity Tag) in the response header for entity data. An ETag is an opaque string indicating the version of a resource - each time a resource changes, the Etag is also modified. This ETag should be cached as part of the data by the client application. The ETag is primarily useful to save bandwidth.

GET /user_management/v1/users/BE14A7269802498F992813885546D058

HTTP/1.1 200 OK
...
Cache-Control: max-age=600, private
Content-Type: text/json; charset=utf-8
ETag: "2147483648"
Content-Length: ...
{ "id": "BE14A7269802498F992813885546D058", "name": "Mustermann" }

The client constructs a GET request containing the ETag for the currently cached version of the resource referenced in an If-None-Match HTTP header:

GET /user_management/v1/users/BE14A7269802498F992813885546D058
If-None-Match: "2147483648"
ETag matches

Return an HTTP response with an empty message body and a status code of 304 Not Modified.

ETag does not match

The data has changed and the web API should return an HTTP response with the new data in the message body and a status code of 200 OK.

Further reading

Find below a list of great articles on the topic Caching

https://www.mnot.net/cache_docs/
http://restcookbook.com/Basics/caching/
http://odino.org/rest-better-http-cache/
https://www.subbu.org/blog/2005/01/http-Caching

Resources for implementation https://github.com/mspnp/azure-guidance/blob/master/API-Implementation.md#considerations-for-optimizing-client-side-data-access

💡 Please give us Feedback which Caching strategy you chose and your experieneces.