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Northwind Labs cut pull-request feedback from 24 to 6 minutes

A Rust monorepo with a 40-minute cold build, brought under control with sccache and native arm64 runners.

24m → 6m
PR feedback
−41%
CI spend
31% → 94%
Cache hit rate

We had convinced ourselves the build was just inherently slow. It was inherently uncached.

Staff engineer, Northwind Labs

Northwind runs a Rust monorepo with about 340 crates. Before migrating, a cold build took 40 minutes and a warm one 24, because target/ was cached on a key that included source files.

What changed

  1. Cache key moved from source hash to Cargo.lock
  2. sccache added with a shared backend, so branches share compiled artefacts
  3. Release builds moved to 16 vCPU arm64 runners
  4. Test suite sharded across four runners by historical duration

The arm64 move was worth 20% on price and about 15% on build time. The cache key fix was worth considerably more than both.

Your next build could be twice as fast, at half the price

Start free. Migrating away is the same one line, and we publish that diff too.