Smaller Rust data structures cut Cloudflare’s DNS cache memory

Cloudflare reduced its DNS cache footprint by changing how immutable entries are represented in Rust. Replacing growable vectors and strings with boxed slices and strings removed unused capacity; combining record lists reduced pointers, and repeated domain names could be inferred instead of stored. The team checked both allocation benchmarks and steady-state memory across production instances.

Cloudflare · Aug 27, 2026

Why it matters

A practical example of profiling data layout before reaching for a different caching architecture.

More context

This August engineering report is older reading. Start by measuring allocation count, padding and unused capacity in your own cache. Cloudflare’s benchmark approximated its record mix, then production measurements checked whether those savings survived real traffic.

Keep in mind

The reported fleet-wide savings depend on Cloudflare’s scale and workload. Immutable storage trades away growth flexibility; 1min has not reproduced the results or established that the same changes help your application.

Original read