Cache settings for REST APIs in API Gateway

You can enable API caching in API Gateway to cache your endpoint's responses. With caching, you can reduce the number of calls made to your endpoint and also improve the latency of requests to your API.

When you enable caching for a stage, API Gateway caches responses from your endpoint for a specified time-to-live (TTL) period, in seconds. API Gateway then responds to the request by looking up the endpoint response from the cache instead of making a request to your endpoint. The default TTL value for API caching is 300 seconds. The maximum TTL value is 3600 seconds. TTL=0 means caching is disabled.

The maximum size of a response that can be cached is 1048576 bytes. Cache data encryption may increase the size of the response when it is being cached.

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Enable Amazon API Gateway caching

In API Gateway, you can enable caching for a specific stage.

When you enable caching, you must choose a cache capacity. In general, a larger capacity gives a better performance, but also costs more. For supported cache sizes, see cacheClusterSize in the API Gateway API Reference.

API Gateway enables caching by creating a dedicated cache instance. This process can take up to 4 minutes.

API Gateway changes caching capacity by removing the existing cache instance and creating a new one with a modified capacity. All existing cached data is deleted.

In the API Gateway console, you configure caching on the Stages page. You provision the stage cache and specify a default method-level cache setting. If you turn on the default method-level cache, method-level caching is turned on for all GET methods on your stage, unless that method has a method override. Any additional GET methods that you deploy to your stage will have a method-level cache. To configure method-level caching setting for specific methods of your stage, you can use method overrides. For more information about method overrides, see Override API Gateway stage-level caching for method-level caching.

When you enable caching within a stage's Cache settings, only GET methods are cached. To ensure the safety and availability of your API, we recommend that you don't change this setting. However, you can enable caching for other methods by overriding method settings.

If you would like to verify if caching is functioning as expected, you have two general options:

Override API Gateway stage-level caching for method-level caching

You can override stage-level cache settings by turning on or turning off caching for a specific method. You can also modify the TTL period or turn encryption on or off for cached responses.

If you change the default method-level caching setting in the Stage details, it doesn't affect the method-level cache settings that have overrides.

If you anticipate that a method that you are caching will receive sensitive data in its responses, in Cache Settings, choose Encrypt cache data.

Use method or integration parameters as cache keys to index cached responses

You can use a method or integration parameter as cache keys to index cached responses. This includes custom headers, URL paths, or query strings. You can specify some or all of these parameters as the cache key, but you must specify at least one value. When you have a cache key, API Gateway caches the responses from each key value separately, including when the cache key isn't present.

For example, suppose you have a request in the following format:

GET /users?type=... HTTP/1.1
host: example.com
...
        

In this request, type can take a value of admin or regular. If you include the type parameter as part of the cache key, the responses from GET /users?type=admin are cached separately from those from GET /users?type=regular.

When a method or integration request takes more than one parameter, you can choose to include some or all of the parameters to create the cache key. For example, you can include only the type parameter in the cache key for the following request, made in the listed order within a TTL period:

GET /users?type=admin&department=A HTTP/1.1
host: example.com
...
        

The response from this request is cached and is used to serve the following request:

GET /users?type=admin&department=B HTTP/1.1
host: example.com
...
        

To include a method or integration request parameter as part of a cache key in the API Gateway console, select Caching after you add the parameter.

Flush the API stage cache in API Gateway

When API caching is enabled, you can flush your API stage's cache to ensure that your API's clients get the most recent responses from your integration endpoints.

To flush the API stage cache, choose the Stage actions menu, and then select Flush stage cache.

Invalidate an API Gateway cache entry

A client of your API can invalidate an existing cache entry and reload it from the integration endpoint for individual requests. The client must send a request that contains the Cache-Control: max-age=0 header. The client receives the response directly from the integration endpoint instead of the cache, provided that the client is authorized to do so. This replaces the existing cache entry with the new response, which is fetched from the integration endpoint.

To grant permission for a client, attach a policy of the following format to an IAM execution role for the user.

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Effect": "Allow",
      "Action": [
        "execute-api:InvalidateCache"
      ],
      "Resource": [
        "arn:aws:execute-api:region:account-id:api-id/stage-name/GET/resource-path-specifier"
      ]
    }
  ]
}            
        

This policy allows the API Gateway execution service to invalidate the cache for requests on the specified resource (or resources). To specify a group of targeted resources, use a wildcard (*) character for account-id, api-id, and other entries in the ARN value of Resource. For more information on how to set permissions for the API Gateway execution service, see Control access to a REST API with IAM permissions.

If you don't impose an InvalidateCache policy (or choose the Require authorization check box in the console), any client can invalidate the API cache. If most or all of the clients invalidate the API cache, this could significantly increase the latency of your API.

When the policy is in place, caching is enabled and authorization is required.

You can control how unauthorized requests are handled by choosing an option from Unauthorized request handling in the API Gateway console.

The three options result in the following behaviors: