When generating a large publication with hundreds or thousands of static articles, build times depend directly on the throughput of your CMS API. Without caching, concurrent requests will saturate database pools and trigger rate limits.

The Caching Pyramid

A resilient headless infrastructure employs a three-tier caching strategy:

1. Application Object Cache (Redis/Memcached): Stores raw SQL query results and post relationship trees in memory inside the WordPress cluster.
2. Response Transient Cache: Serializes computed REST JSON payloads so complex tax queries and custom field aggregations execute only once per publish event.
3. Edge CDN / Reverse Proxy: Cloudflare or Fastly caches the public API endpoints, serving requests without ever reaching the origin server.

Stale-While-Revalidate in Action

Using standard HTTP cache-control headers allows frontends to receive instant cached responses while the edge updates stale content in the background:

Cache-Control: public, max-age=3600, stale-while-revalidate=86400
ETag: W/"33a64df551425fcc55e4d42a148795d9f25f89d4"

Instant Cache Invalidation

The hardest problem in computer science is cache invalidation. In headless WordPress, this is solved by hooking into the save_post action hook. When an editor clicks "Update", the API studio invalidates the specific post cache and purges the corresponding CDN URL.