Why we moved our build to Bazel

Our monorepo had grown to 1.4 million lines of code, and a clean CI build took 47 minutes. Incremental builds were unreliable, so engineers ran clean builds out of habit.

What we tried first

1. Caching node_modules between CI runs
2. Splitting the test suite across 12 shards
3. Upgrading CI runners to 32 cores

Each change helped a little, but none fixed the root problem: the build had no accurate dependency graph.

Results

After the migration, the median CI build takes 6 minutes, and 92% of builds hit the remote cache.

Thanks to the developer productivity team for leading the migration.

Jordan Alvarez is a staff engineer on the platform team.