Waiting 14 minutes for a Windows CI job kills developer flow. For our Model Context Protocol server (Sentinel-IR-MCP), we refused to tolerate that bottleneck anymore.
Here is exactly how we optimized our Windows test suite across Node 20, 22, and 24, dropping the total job runtime to 2 minutes and 44 seconds without sacrificing a single check.
Source (GitLab, Apache-2.0): https://gitlab.com/jakubrojicek11/sentinel-ir-mcp
Package (npm): https://www.npmjs.com/package/sentinel-ir-mcp
The analyzer behind it: https://www.npmjs.com/package/sentinel-ir
The Bottleneck (GitLab Shared Windows Runners)
A standard run on GitLab SaaS Windows took 13.6 minutes, even though our 118 unit tests executed in just 1.6 minutes. The rest was pure infrastructure drag:
• VM Provisioning: 3.5 minutes (unfixable)
• Real-time Antivirus: Windows Defender choked on npm ci and execution scripts, dragging out our compat-smoke test to 2.9 minutes.
The Fix: Strategic Split & Target Optimization
Instead of fighting the slow runner environment, we re-architected where and how the jobs run:
- Shifted Dev Push Matrices to GitHub Actions: GitHub's windows-latest images spin up in seconds (1–2 s) instead of minutes.
- Built-in Security Clearance: Real-time scanning (RealTimeProtectionEnabled) is off by default on GitHub's native dev images. This instantly cut our compat-smoke step down to seconds.
- Smart Caching & Selective Runs: We enabled direct Node/npm caching and added strict rules to completely skip the Windows matrix if a commit only modifies the README.md.
- Kept GitLab strictly for Releases: The heavy GitLab Windows job was moved to run only on release tags as a final gate before publishing to npm.
The Result
Step (Node 24) Old GitLab Pipeline New GitHub Actions Pipeline
VM Boot / Wait ~3.5 min 1–2 s
npm ci 84 s 4–9 s
Test Execution 95 s 22–28 s
Total Job Time 13.6 min 2.7 min
The code quality remains identical. All 118 tests run flawlessly across all Node versions, but now the feedback loop takes less than 3 minutes.
If your Windows pipelines are killing your productivity, look closely at VM spin-up times and real-time antivirus hooks. The performance lift is hiding right there.
