Enabling API caching to enhance responsiveness

You can enable API caching in Amazon 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.

Note

Caching is best-effort. You can use the CacheHitCount and CacheMissCount metrics in Amazon CloudWatch to monitor requests that API Gateway serves from the API cache.

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.

This is a HIPAA Eligible Service. For more information about AWS, U.S. Health Insurance Portability and Accountability Act of 1996 (HIPAA), and using AWS services to process, store, and transmit protected health information (PHI), see HIPAA Overview.

Important

When you enable caching for a stage, only GET methods have caching enabled by default. This helps to ensure the safety and availability of your API. You can enable caching for other methods by overriding method settings.

Important

Caching is charged by the hour based on the cache size that you select. Caching is not eligible for the AWS Free Tier. For more information, see API Gateway Pricing.

Enable Amazon API Gateway caching

In API Gateway, you can enable caching for a specified 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.

Note

The cache capacity affects the CPU, memory, and network bandwidth of the cache instance. As a result, the cache capacity can affect the performance of your cache.

API Gateway recommends that you run a 10-minute load test to verify that your cache capacity is appropriate for your workload. Ensure that traffic during the load test mirrors production traffic. For example, include ramp up, constant traffic, and traffic spikes. The load test should include responses that can be served from the cache, as well as unique responses that add items to the cache. Monitor the latency, 4xx, 5xx, cache hit, and cache miss metrics during the load test. Adjust your cache capacity as needed based on these metrics. For more information about load testing, see How do I select the best API Gateway cache capacity to avoid hitting a rate limit?.

In the API Gateway console, you configure caching in the Settings tab of a named Stage Editor.

To configure API caching for a given stage:

1. Go to the API Gateway console.

2. Choose the API.

3. Choose Stages.

4. In the Stages list for the API, choose the stage.

5. Choose the Settings tab.

6. Choose Enable API cache.

7. Wait for the cache creation to complete.

Note

Creating or deleting a cache takes about 4 minutes for API Gateway to complete. When a cache is created, the Cache status value changes from CREATE_IN_PROGRESS to AVAILABLE. When cache deletion is completed, the Cache status value changes from DELETE_IN_PROGRESS to an empty string.

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:

• Inspect the CloudWatch metrics of CacheHitCount and CacheMissCount for your API and stage.

• Put a timestamp in the response.

Note

You should not use the X-Cache header from the CloudFront response to determine if your API is being served from your API Gateway cache instance.

Override API Gateway stage-level caching for method caching

You can override stage-level cache settings by enabling or disabling caching for a specific method. By increasing or decreasing its TTL period; or by turning encryption on or off for cached responses.

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

To configure API caching for individual methods using the console:

1. Sign in to the API Gateway console at https://console.aws.amazon.com/apigateway.

2. Go to the API Gateway console.

3. Choose the API.

4. Choose Stages.

5. In the Stages list for the API, expand the stage and choose a method in the API.

6. Choose Override for this method in Settings.

7. In the Cache Settings area, you can set or clear Enable Method Cache or customize any other desired options. (This section is shown only if stage-level caching is enabled.)

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

When a cached method or integration has parameters, which can take the form of custom headers, URL paths, or query strings, you can use some or all of the parameters to form cache keys. API Gateway can cache the method's responses, depending on the parameter values used.

Note

Cache keys are required when setting up caching on a resource.

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, you choose the Flush entire cache button under the Cache Settings section in the Settings tab in a stage editor of the API Gateway console.

Note

After the cache is flushed, responses are serviced from the integration endpoint until the cache is built up again. During this period, the number of requests sent to the integration endpoint may increase. This may temporarily increase the overall latency of your API.

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.

Note

Cross-account cache invalidation is not supported.

{
  "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 an 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 Handle unauthorized requests in the API Gateway console.

The three options result in the following behaviors:

• Fail the request with 403 status code: returns a 403 Unauthorized response.

  To set this option using the API, use FAIL_WITH_403.

• Ignore cache control header; Add a warning in response header: process the request and add a warning header in the response.

  To set this option using the API, use SUCCEED_WITH_RESPONSE_HEADER.

• Ignore cache control header: process the request and do not add a warning header in the response.

  To set this option using the API, use SUCCEED_WITHOUT_RESPONSE_HEADER.