A day in the life of 2,000 developers
summary
Stripe runs a ~25M-line Ruby monorepo with 1.5 million tests that would take two months on one machine, so CI uses file-access tracing (LD_PRELOAD now, moving toward eBPF) to map tests to files and cut runs to ~1,000–2,000 tests — a 99.5% reduction with ~1% flake. Tooling includes Sorbet types, VS Code LSP, a Rust rubyfmt and rubocop. Merges use integration branches and deploys use blue‑green traffic shifts, enabling traffic-shift rollback in 1s.
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chapters (14)
- 0:00Introduction and context
- 1:03Who is Stripe and what it does
- 2:49Debugging a currency issue in production
- 7:23Benefits of static type checking
- 9:07Running CI at massive scale
- 12:57Smart test selection for CI
- 17:11Integration branches for safe merges
- 19:37Q&A begins
- 20:00Optimizing container builds
- 22:07QA and pre-production testing
- 24:51Automated traffic shifting in production
- 25:53Optimizing Ruby process startup
- 27:14Upgrading to Ruby 3.3 and YJIT
- 28:36Closing remarks and Q&A
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