Two years ago, I joined a team that was migrating a monolithic Rails application to microservices. We made every mistake in the book. Here are the five most important lessons I learned.
Lesson 1: Start with a Strong Domain Model
We started by splitting services based on technical layers — API, business logic, data access. This was a disaster. Services should be split by business capability. We refactored into Order Service, User Service, and Payment Service. Everything became cleaner.
Lesson 2: Data Consistency is the Hardest Part
In a monolith, transactions are easy. In microservices, they are not. We learned to use the Saga pattern for distributed transactions. Each service handles its own local transaction and publishes events to trigger the next step.
Lesson 3: Observability is Non-Negotiable
You cannot debug what you cannot see. We set up Prometheus for metrics, Grafana for dashboards, and Jaeger for distributed tracing. Without these, we would have been flying blind.
Lesson 4: Fail Fast, Fail Gracefully
We implemented circuit breakers using Resilience4j. When a downstream service is slow, we fail fast and return a fallback response instead of letting the timeout cascade through the system.
Lesson 5: Don’t Over-Engineer
Not every service needs to be a microservice. We kept a few services as monoliths because the complexity of splitting them was not worth the benefit. Pragmatism beats purity.
Final Thought
Microservices are a tool, not a goal. If your team is not ready for the operational complexity, do not do it.