Policy execution order

This policy runs after every request and response policy.

Known issues

Both the HTTP Cache Response and HTTP Retry Rules fail to evaluate expressions. As a result, the When this policy should be applied field should not be set. Doing so can cause issues with the way the policy is applied.

Architecture

Each Snaplex node has its own cache, so the cache for an incoming request might be missed on each node until properly distributed and hydrated on each node.

By default, the following cache keys are used:

• Protocol
• Host
• Path
• HTTP Method

The policy supports incorporating headers and query parameters as part of the cache key (not to access the cache key). The headers and query parameter values are used as part of the generated cache key to ensure unique cache entries as needed.

Usage guidelines

• We limit each policy to store 100 entries in the cache per policy. Accordingly, the policy evicts the least used entry after 100.
• Expired caches cannot be accessed, and new entries overwrite any existing ones. In the default configuration, each response cache can store up to 85.83 MB of payload data.

Best Practices

• Do not use any headers and query string parameters, like a timestamp, as part of your cache key, or it will never result in a fulfilled request. You can optionally remove those headers using the Request Transformer policy. Or, avoid headers query string parameters as part of the cache key and only as needed when a unique value is present per request.
• To invalidate cached data, use the Invalidate Response Cache API. The Invalidate Response Cache API enables you to keep cached data up to date with the latest changes. You can define caching policies for the specific API endpoint, specifying parameters such as cache duration, cache key generation, and cache storage. The cache invalidation mechanism monitors changes in the data source and updates the cache as configured to ensure data consistency.

Limitations

• Each response cache can only contain 85 MB. The policy always returns the response, but any data over the limit renders the payload incomplete without notice.
• A response cache is not effective to use for POST and PUT HTTP methods because these operations are meant to alter the state of data, and therefore should not be cached.