In Q1 2026, our 12-person engineering team migrated 47 production repos from CircleCI 7.2.1 to GitLab CI 17.4.0, slashing median build times from 14 minutes 22 seconds to 6 minutes 17 seconds — a 56.3% reduction that saved 1,200+ developer hours annually and $42k in CI runner costs. We didn’t just flip a switch: we benchmarked every pipeline stage, rewrote 142 custom CircleCI orbs to GitLab components, and fixed 3 critical cache invalidation bugs in the process. Here’s the unvarnished retrospective, complete with runnable code, benchmark data, and hard-learned lessons for teams considering the same move.

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