From Monolith to Microservices: Lessons Learned

Over the past few months, I've been migrating a legacy Java EE monolith into a microservices ecosystem. This post shares lessons learned, key decisions, and technical pitfalls to avoid when tackling such a refactor.

1. Refactor for Interfaces First

Begin by extracting service interfaces and domain logic into modular components. This separation helps prepare the codebase for service decomposition.

2. Observability Before Scale

Ensure every service emits logs, metrics, and traces. A robust observability stack (I used Prometheus, Jaeger, OpenTelemetry) helps diagnose issues early.

3. CI/CD Pipelines Are Non-Negotiable

Introduce GitLab or Jenkins pipelines early. Each microservice should be independently deployable with Helm or Kustomize.

Read more on my Observability Stack or view the Microservices Project.