This is really it. You can have everything in a monolith and scalable and modular by following good architectural practices. If the need arises, you could move

This is really it. You can have everything in a monolith and scalable and modular by following good architectural practices. If the need arises, you could move into SOA, and break out a couple of your larger domain modules. Continue following these same rules though. If the need arises still, you could move into micro services, and break out more / all of your domain modules. Truly understand first whether you actually need this first. But the "let's do micro services this monolith is old junk" trope, abandonwaring the codebase, building out a bunch of services without strong, fundamental domain knowledge, and then complaining when shit is expensive and fragile and broken- it's getting tiring.