Fastly Surrogate Keys: A Better Way to Purge API Caches
Fastly's edge caching with Surrogate-Key headers allows for fine-grained purging, enabling you to cache aggressively and invalidate only what changed.
Caching API responses at the edge is appealing until the issue of invalidating cache becomes problematic. Balancing between caching aggressively and purging selectively is crucial. Fastly provides a solution to this challenge. By creating a Fastly service and pointing it to your API as the origin, you can manage caching effectively.
Surrogate-Key header is introduced, allowing API responses to be tagged with one or more keys. This tagging enables Fastly to index the cached object under all keys, offering fine-grained purging controls. When data changes, only the relevant keys need to be purged, leading to targeted cache invalidation. While other AWS services like CloudFront and API Gateway also offer caching capabilities, they lack the surrogating key functionality and key-based purging, which restricts their ability to provide precise, event-driven invalidation.
Fastly on the other hand, provides a free tier, enabling users to set up multiple projects without incurring costs. The key to edge caching success is fine-grained purging, which ensures data remains fast and fresh.
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