CDN and Edge Caching for APIs

For customers far from an API's servers, the network journey can account for a meaningful part of the wait. Consider a bookstore serving several continents from one origin region. Its public book descriptions change infrequently, yet every read travels to the origin. Moving reusable responses closer to customers can reduce both waiting and origin traffic. Moving a customer-specific response into that same shared cache can expose private data.

A content delivery network can cache API responses as well as static files, but safe reuse requires an explicit contract.

This chapter covers which requests and responses the edge may cache, cache keys, freshness, revalidation, purging, origin protection, and rollout verification. The examples use a fictional bookstore at api.bookstore.example; cache rules and timing choices are illustrative.