I was part of a project that did exactly this - same monolithic code base with config flags that transformed it into web server, worker or scheduler. It allows

I was part of a project that did exactly this - same monolithic code base with config flags that transformed it into web server, worker or scheduler. It allows scaling all parts separately, but I can confirm it's easy to introduce bugs if you're not careful. Since you're sharing the same DB, migrations also need to be backwards-compatible. A cool side-effect is that you can usually run the whole thing in one app for development by just enabling all profiles - as opposed to some microservice architectures where you need dozens of containers and DBs for replicating inter-service bugs.