Cutting CI Pipeline Time by 64%: What Actually Works in Production
Platform Engineering, Tuesday, September 22nd, 2026
An engineering manager details how his team cut CI pipeline time from an hour to 22 minutes while growing test coverage 90%.
An engineering manager at retailer M&S details how his team cut Merge Train CI pipeline duration by 64%, from roughly an hour to 22 minutes, while growing test coverage 90% and cutting the failure rate from 18% to single digits, for only a 10% rise in monthly compute cost.
The biggest lever was migrating compute instances from C5 to C7i processors; AMD was rejected despite lower cost due to high execution-time variance.
Other wins came from segregating browser tests from service tests to cut container overhead, and using automated logging plus LLM analysis to quarantine flaky tests.
The guiding principle: "intuition cannot beat data" - they changed one variable at a time, estimating a $65,000 monthly productivity gain.