Optimizing Our E2E Pipeline

This post details the optimization of Slack's E2E testing pipeline by implementing conditional frontend builds using `git diff` to detect changes and reusing prebuilt assets served via an internal CDN. This reduced frontend build frequency by 60% and average build time from ~5 minutes to ~2 minutes, saving thousands of hours and terabytes of storage monthly. It also led to more reliable E2E results and the rediscovery of legacy code.