I run a local Valhalla build cluster to power the https://sidecar.clutch.engineering routing engine. The cluster runs daily and takes a significant amount of wall-clock time to build the entire planet. That's about 50% of my CI time; the other 50% is presubmits + App Store builds for Sidecar + CANStudio / ELMCheck.

Using GitHub actions to coordinate the Valhalla builds was a nice-to-have, but this is a deal-breaker for my pull request workflows.

Cool, that looks a lot nicer than the OBD scanner app I've been using.

On ZeroFS [0] I am doing around 80 000 minutes a month.

A lot of it is wasted in build time though, due to a lack of appropriate caching facilities with GitHub actions.

[0] https://github.com/Barre/ZeroFS/tree/main/.github/workflows

ZeroFS looks really good. I know a bit about this design space but hadn't run across ZeroFS yet. Do you do testing of the error recovery behavior (connectivity etc)?

This has been mostly manual testing for now. ZeroFS currently lacks automatic fault injection and proper crash tests, and it’s an area I plan to focus on.

SlateDB, the lower layer, already does DST as well as fault injection though.

I found that implementing a local cache on the runners has been helpful. Ingress/egress on local network is hella slow, especially when each build has ~10-20GB of artifacts to manage.

What do you use for the local cache?

Just wrote about my approach yesterday: https://jeffverkoeyen.com/blog/2025/12/15/SlotWarmedCaching/

tl;dr uses a local slot-based cache that is pre-warmed after every merge to main, taking Sidecar builds from ~10-15 minutes to <60 seconds.

Wow, that's a very cool project.

Thank you!

1 hour build/test time, 20 devs, that's 50 runs a month. Totally possible.

GH actions templates don’t build all branches by default. I guess it’s due to them not wanting the free tier to use to much resources. But I consider it an anti-pattern to not build everything at each push.

That is because GH Actions is event based, that is more powerful and flexible than just triggering on every push and not letting it be configured.

``` on: push ```

is the event trigger to act on every push.

You'll waste a lot of CI on building everything in my opinion, I only really care about the pull request.