In this ever evolving world of software development I want to rephrase a very clichéd statement — “Change is the only constant”. Kind of stating the obvious here, but… it’s a nice introduction for the topic we’re about to explore.
Services allow for teams to work independently on parts of the system. Again, you can do this in a monolith. I have done this in a monolith. But the challenge with monolith (and a related challenge with services in a monorepo (single source repository)) is that humans struggle to tangibly understand domains that are theoretically separate when they are presented as colocated by the source code. If I can see all of the code and it all compiles together and feels like a single thing, my tendency is to want to use it as a single thing. Grab code from here to use there, grab data from there to use here, etc.