What was the most difficult and most interesting part of migrating from monolith to microservices?

The most challenging aspect of migrating from a monolith to microservices is usually organizing interaction between services and managing distributed transactions. It is necessary to think about how services will communicate — via REST, gRPC, or messages, how to ensure data consistency and error handling in a distributed system.

The most interesting part becomes the ability to scale individual parts of the system independently, improve fault tolerance, and accelerate development through separation of responsibilities. It is also interesting to build CI/CD for each microservice and observe how the system becomes more flexible and adaptive to changes.