Bazel Monty Demo — 121s cold build, 15.7s fully cached

Bazel 9.1.1 / rules_rust / Remote Cache / Remote Execution

Monty, rebuilt as a Bazel remote build.

Monty is a minimal<br>Python interpreter written in Rust, from the Pydantic team. This demo<br>Bazelizes a pinned upstream archive with a small patch overlay — no<br>fork — and takes it from local build to remote cache to remote<br>execution. Every number below is committed as JSON, with the scripts<br>to reproduce it.

121.1s → 15.7ssame build, fully cached

Read the E2E write-up<br>Raw numbers (JSON)<br>View the repo

Measured, not estimated

Two fresh Bazel output bases against one bazel-remote<br>instance in Docker. The seed run populates the cache; the reader run<br>consumes it with uploads disabled. No local action cache involved.<br>To be precise about what is measured: this compares a cold full build<br>(with cache upload) to a fully cached rerun of the same targets —<br>both with --remote_download_toplevel.

121.135s<br>Cold seed run — build + test, 756 processes, 0 remote cache hits.

15.706s<br>Reader run — same targets, fresh output base, uploads disabled.

432 / 432<br>Every executable action on the reader run came from the remote cache. The other 325 processes are Bazel-internal and never cacheable.

120.287s<br>Clean Islo sandbox build of //:monty_cli, 1302 processes.

1.719s<br>//:core_tests pass in the Islo sandbox run.

5m01s / 17s<br>Reference GitHub CI run and GitHub Pages deploy, both green.

seed (cold cache)121.135s

reader (warm cache)15.706s

Bazel 9.1.1, Crabbox 0.36.0, Monty pinned at 4bcbcf5.<br>Islo is Incredibuild's cloud sandbox service; this demo is an<br>Incredibuild project. Full summary in<br>docs/metrics/e2e-results.json.

01<br>Pin

Fetch Monty at commit 4bcbcf5 and apply a reviewable overlay patch — no fork.

02<br>Build

Use Bzlmod, rules_rust, and Cargo metadata mirrored under third_party/.

03<br>Prove

Run the local seed/reader cache demo with Docker, then provider cache and remote-execution stages in Islo sandboxes.

Commands

bazelisk build //:monty_cli<br>bazelisk test //:core_tests<br>./scripts/run_local_demo.sh<br>./scripts/run_islo_demo.sh