How do Web developers manage the consistency of dynamic content using ESI?
ESI provides a number of ways to manage the consistency (freshness) of cached objects, including the ability to define expiration policies. Due to the unpredictable nature of frequently changing content, ESI also includes a content invalidation specification. The invalidation specification is used by syndication servers, content management systems, databases, custom scripts, application logic, etc. to send HTTP-based invalidation messages to a local cache and/or delivery network. The invalidation message tells the cache or delivery network to overwrite the metadata associated with particular ESI objects residing on edge servers. A combination of the two approaches (expiration, invalidation) and some simple fragment naming conventions can be used to ensure that the content delivered from the edge is always consistent.
