Turborepo is a tool that came across my virtual desk recently. Monorepo develoment has been around for a long time. This is a strategy where all of your code remains in one repository regardless of services. A lot of people use monorepo's even for microservices. The huge upside is to keep everything in one place, which allows for development efficiency, such as grepping an entire codebase for specific keywords. A quick example would be a top level directory which has child directories that each contain an npm package, unlike publishing these packages, you access them locally as though they were published.
Building a remote cache server for Turborepo