# How Stripe Selectively Executes Tests in a 50-Million-Line Ruby Monorepo

DevFeed: [How Stripe Selectively Executes Tests in a 50-Million-Line Ruby Monorepo](<https://devfeed.tech/articles/how-stripe-runs-a-50m-lines-monorepo-with-0-pain-18128.md>)

Original publisher: [Read original article](<https://hungrymindsdev.substack.com/p/how-stripe-runs-a-50m-lines-monorepo>)

Author: Alexandre Zajac

Published: 2026-06-08T15:30:11Z

Content type: article

Language: en

Sources: [Hungry Minds](<https://devfeed.tech/sources/hungry-minds.md>)

Topics: [stripe](<https://devfeed.tech/topics/stripe.md>), [Software Engineering](<https://devfeed.tech/topics/software-engineering.md>), [Ruby](<https://devfeed.tech/topics/ruby.md>), [C++](<https://devfeed.tech/topics/c-plus-plus.md>)

Tags: [c-plus-plus](<https://devfeed.tech/tags/c-plus-plus.md>), [dependencies](<https://devfeed.tech/tags/dependencies.md>), [monorepo](<https://devfeed.tech/tags/monorepo.md>), [performance](<https://devfeed.tech/tags/performance.md>), [ruby](<https://devfeed.tech/tags/ruby.md>), [stripe](<https://devfeed.tech/tags/stripe.md>)

## AI overview

Stripe built Selective Test Execution to run only the tests affected by changes in its 50-million-line Ruby monorepo. The system uses runtime file-access interception, dependency indexes, and guardrails to reduce test execution while maintaining code-safety confidence.

## Source excerpt

PLUS: Index design fundamentals 👨💻, KV performance tool ⚡, Null bugs cost billions 💰