How we sharded our test suite for 10x faster runs on GitHub Actions

EdgeDB, a company that uses GitHub Actions for its CI workflow consisting of thousands of tests and various build processes, has managed to reduce the runtime from 2+ hours to just 10 minutes by sharding their test suite across several workers. They achieved this by evenly splitting up their 5000-ish tests into separate "shards" using GitHub's build matrix feature. The algorithm they used for sharding takes into account the setup conundrum and ensures that no single slow-poke delays the whole run. This approach allowed them to distribute the workload across multiple workers, significantly speeding up their CI process.