Optimizing Our E2E Pipeline

Slack's DevXP team optimized their E2E testing pipeline by eliminating redundant frontend builds, reducing build times by 50% and build frequency by 60%.

• •Frontend builds (~5 min) were triggered even when no frontend code changed, wasting time across hundreds of daily PRs
• •Used `git diff` with 3-dot notation to detect frontend changes against main branch, skipping builds when unnecessary
• •Reused prebuilt frontend assets from AWS S3 via an internal CDN when no frontend changes were detected
• •Change detection and artifact lookup completed in under 3 seconds on average, even across 100,000+ tracked files
• •Combined with a prior Webpack upgrade, average E2E pipeline build time dropped from ~10 minutes to ~2 minutes, saving terabytes of S3 storage monthly