How Blacksmith Made Our CI More Than Twice as Fast
We moved our CI to Blacksmith runners in October. Our main pipeline went from a median of 8.5 minutes to under 4. Here is how the switch went.
Caliplaces is a small team building an app for the calisthenics and street workout community, where parks, athletes and coaches come together in one place. Everything we build lives in one repository, so our CI runs on almost every change we make. When CI is slow, everything is slow.
In October we moved our GitHub Actions workflows to Blacksmith runners. This post covers why we did it, how long the switch took, and what changed.
Why we switched#
Our main CI pipeline was taking around eight and a half minutes per run. That doesn't sound like much until you count how many times a day it runs. Every pull request, every fix, every small tweak meant waiting for the checks to finish before we could merge and move on. For a team our size, those minutes add up fast and they break focus.
How long the switch took#
Not long. Moving a workflow to Blacksmith is basically a one-line change: you swap the runner label your job runs on. We moved our main pipeline first on October 18, watched it for a while, and then moved the rest of our workflows once we were happy with it.
The results#
We compared our main CI pipeline on standard GitHub runners against its first week on Blacksmith, using successful runs only.
| Metric | GitHub runners | Blacksmith |
|---|---|---|
| Median main CI run | 8 min 30 s | 3 min 56 s |
| Two near-identical runs, right before and after the switch | 8 min 29 s | 5 min 13 s |
| Build step alone | 42 s | 15 s |
That's a median run more than twice as fast, measured over 16 runs on GitHub runners and 97 runs in our first week on Blacksmith.
To be fair about the numbers: since then we have added more tests and extra checks to the pipeline, so a typical run today takes longer than it did in that first week. That's our test suite growing, not the runners slowing down, and it's exactly why faster runners matter to us.
What it means for Caliplaces users#
Faster CI means we can ship fixes and new features sooner. When someone reports a problem with a park on the Caliplaces app, we spend less time waiting on checks and more time getting the fix out.
Thanks, Blacksmith#
Blacksmith supports early-stage teams through its startup program, and we're grateful to be part of it. If your CI feels slow, it's worth a try. The switch is small and easy to roll back if it isn't for you.