Why not a monolith? You have no complex logic, microservices are harder to deploy. Making 4 programs with 3 classes on each is the worst idea. Oh, no, make 50 classes, cause every function needs it's own class.

This architecture isn't good for this program. Even if you have to balance loads, you can make it without of microservices.

I'm making Minecraft hosting, I need microservices, cause making containers and game servers may be done at different servers, central microservices must be isolated, because docker is not very safe. Making orders, register users, are really independent tasks. Web interface must be isolated from DB, it is made by other programmer.

But here you divide your system into 4 components, when you can make one small project. Microservices don't mean 1-2 functions per app, they mean 1-2 tasks, separate from other modules