I’m still hoping some standard toolset emerges for dealing with large monorepos sometime in the near future. At the moment it’s clear that a number of companies are rolling their own solutions, which follow one of two patterns:

- Persistent process which watches workspace changes, or

- Workspace in virtual filesystem.

The other common factor seems to be trunk-based development with all commits rebased into a linear history. I’m not super hopeful that we’ll see an open-source solution in this space for a while, though—any company with a code base large enough to really need these solutions is also large enough to throw a few engineers at VCS, especially given that they’d already have engineers supporting VCS from the operations side of things.