Bijoy Choudhury builds a process:
In any microservices migration, extracting services from all their dependencies and point-to-point integrations carries the most risk. If you feel hesitant about decomposing your application, that hesitation is justified. The first service extraction is uniquely challenging because you have to examine years of accumulated technical debt and unresolved organizational decisions at the same time.
That’s why the objective for the first service extraction should not focus on achieving immediate scalability or to redefine organizational practices but to validate a narrow capability. Instead, it’s about identifying a discrete unit of functionality that can be isolated, deployed independently, and integrated with the existing system without rewriting the entire system or introducing instability.
There’s some good advice in here, as well as one reason why I’m not totally sold on microservices: the isolation of databases. This sounds great until you’re hitting seven different services to retrieve data 100x slower than a simple SQL query would have been because you have complex filtering criteria across these seven services. And then you build an extra layer of caching, introducing even more complexity to solve a problem that never needed to exist.