Support two projects build in the same repo

I am trying to create a build for two projects in my repo, on for frontend and one for a backend,
I added two builds to my circle ci yaml file each working in a different “working directory”
but the build fails on caching stage and on installing.
What is the right configuration to support this?

Thanks.

I’ve not done this, but there have been a lot of questions here about this in the past. Search for “monorepo” in the forum.