Aurora — a programmable edge cache

The problem

Our origin was buckling under read-heavy traffic with long invalidation tails. Off-the-shelf CDNs gave us caching but no programmable control over what to invalidate, when, and where.

Approach

We built a cache layer on Cloudflare Workers with Durable Objects as the coordination primitive. Invalidation became a first-class, rule-driven operation expressed in a small DSL, evaluated at the edge in Rust compiled to WASM.

Outcome

p99 dropped 62%, origin load fell by an order of magnitude, and product teams could express cache policy as code reviewed in the same PR as the feature.