Cloudflare shrinks its hash rings to reclaim 100 TB of RAM

Cloudflare reduced memory used by its request-routing hash rings by storing entries more compactly and generating fewer hashes per server. The team reports reclaiming more than 100 TB of RAM across its fleet. Its analysis found that extra hashes offered diminishing balance improvements and, at high counts, collisions could actually make distribution worse.

Cloudflare · Sep 18, 2026

Why it matters

A practical example of checking both data layout and algorithm assumptions before buying more capacity.

More context

The Rust implementation packs each entry into six bytes instead of eight. Rollout temporarily kept both ring versions, moving traffic by request hash and data center to control cache churn. The implementation is available behind a feature in pingora-ketama; try it with representative traffic and a migration plan.

Keep in mind

The fleet savings are Cloudflare’s measurements, not a reproduced benchmark. Changing routing can miss warm caches and increase origin traffic; smaller rings need workload-specific validation.

Original read