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.

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.

Wow, that's a very cool project.

Thank you!