RESTful Web Services - Caching

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Caching refers to storing the server response in the client itself, so that a client need not make a server request for the same resource again and again. A server response should have information about how caching is to be done, so that a client caches the response for a time-period or never caches the server response.

Following are the headers which a server response can have in order to configure a client's caching −

Sr.No.	Header & Description
1	Date Date and Time of the resource when it was created.
2	Last Modified Date and Time of the resource when it was last modified.
3	Cache-Control Primary header to control caching.
4	Expires Expiration date and time of caching.
5	Age Duration in seconds from when resource was fetched from the server.

Cache-Control Header

Following are the details of a Cache-Control header −

Sr.No.	Directive & Description
1	Public Indicates that resource is cacheable by any component.
2	Private Indicates that resource is cacheable only by the client and the server, no intermediary can cache the resource.
3	no-cache/no-store Indicates that a resource is not cacheable.
4	max-age Indicates the caching is valid up to max-age in seconds. After this, client has to make another request.
5	must-revalidate Indication to server to revalidate resource if max-age has passed.

Best Practices

Always keep static contents like images, CSS, JavaScript cacheable, with expiration date of 2 to 3 days.
Never keep expiry date too high.
Dynamic content should be cached for a few hours only.

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