Configure caching behavior

Media CDN serves content as close to users as possible by using Google's global edge caching infrastructure to cache content and reduce load on origin infrastructure.

You can control how content is cached for each route. This lets you optimize behavior based on the type of content, client request attributes, and your freshness requirements.

Cacheability

The following sections describe what responses Media CDN caches and how to improve cache offload.

Default caching behavior

By default, the following cache-related settings apply to each Edge Cache service:

• Default cache mode of CACHE_ALL_STATIC:

  • Respects origin cache directives, such as Cache-Control or Expires, up to a configurable max TTL.
  • Caches static media types automatically with a default TTL of 3600s, if no origin cache directives are present.
  • Caches HTTP 200, 204, and 206 status codes (negative caching is not enabled).

• Does not cache responses that have no-store or private cache-control directives or that are otherwise uncacheable.

Responses that are not static content or that are missing valid cache directives are not cached unless caching is explicitly configured. To learn how to override the default behavior, see the documentation on cache modes .

The default behavior is equivalent to the following cdnPolicy. Routes without an explicit cdnPolicy configured behave as if they have the following configuration:

cdnPolicy:
  cacheMode: CACHE_ALL_STATIC
  defaultTtl: 3600s
  cacheKeyPolicy:
    includeProtocol: false
    excludeHost: false
    excludeQueryString: false
  signedRequestMode: DISABLED
  negativeCaching: false

Cacheable responses

A cacheable response is an HTTP response that Media CDN can store and quickly retrieve, thus allowing for faster load times. Not all HTTP responses are cacheable.

You can configure cache modes for each route to override this behavior (for example, using the CACHE_ALL_STATIC cache mode to cache common media types) even if the origin does not set a cache control directive in the response.

Requests and responses that meet the criteria defined in uncacheable responses supersedes cacheability.

The following table describes the requirements to cache particular HTTP responses. Both GET and HEAD responses must adhere to these requirements.