At Jasp, we're using a monorepo. Which means the source code of shared dependencies is in the same place as the apps that use them. We needed a tool to automate some of the tasks you usually do in a monorepo, such as building, testing, linting, typechecking. Being able to make sure you didn't break anything anywhere in the app with a simple command instead of waiting for a CI run makes our team more productive.

The fact that it does this in an optimized way, fetching results from previous runs if the source code has not changed, feels extremely satisfactory, since you can run a typechecking command on all your packages, but only those that have changed will actually get typechecked.