Consistency

Synopsis Multi-CDN caches do not become consistent automatically. The same request can produce different objects when providers use different cache keys, default TTLs, purge semantics, or origin headers. Consistency requires one explicit policy, equivalent provider configurations, safe deployment order, and verification at more than one edge. Operational checklist Define one cache-key specification for hosts, paths, query strings, headers, and cookies. Return explicit Cache-Control and validator headers from the origin. Use content-addressed or versioned URLs for static assets. Keep temporary 404 and 5xx caching short and consistent. Translate one purge intent into the narrowest supported operation at every provider. Record provider request identifiers, completion state, and elapsed time. Verify response bytes, Age, validators, and cache-status headers from representative regions. Keep old immutable assets available during rollback. Test the policy whenever a provider or origin layer changes. Purpose and scope Multi-CDN changes cache behavior because different networks fetch, store, and expire objects using different rules and clocks. The goal is that users receive the same bytes for the same URL regardless of the serving CDN and that changes reach users in a controlled and explainable way. The guidance applies to static assets and dynamic responses that allow caching. It also covers the surrounding systems that push and purge content. ...