QA Automation1 min read
Parallel Sharding Playwright Suites in CI Without Flaky Lottery
By Priyatham Rama Sai
Even splits by file count starve some workers while others idle when spec times vary wildly. Sharding by historical duration halved wall-clock time on a commerce client’s regression without new hardware.
Data-driven split
Capture per-spec duration from last N runs. Rebalance shards when suites grow — quarterly is enough for most teams.
Isolation
Workers need unique auth, storage, or API keys so parallel runs do not step on each other — flakiness returns if you only parallelize blindly.
CI integration
Expose shard index and total to runners. Fail fast on infrastructure errors vs test failures — retry policies differ.