Introduction
Every engineering team hits a wall. A moment when your once-beautiful monolith becomes a bottleneck—slow deployments, fragile code, and team conflicts. We hit that wall too. This is the story of how we broke our monolith, one service at a time, and built a scalable microservices architecture from scratch.
The Monolith – When Simplicity Becomes a Curse
Our legacy system was built fast, as a proof-of-concept that became production. Over time, a single Java Spring Boot codebase managed everything—from authentication to payment processing.
The result?
- One change = risk to everything
- Long build & deployment cycles
- Developer gridlock in version control
- Scaling the entire app for one small feature
Why We Decided to Refactor
The pain was real. Features took weeks, bugs were hard to isolate, and we couldn’t scale individual components. We needed to:
- Decouple dependencies
- Scale horizontally
- Deploy independently
- Improve CI/CD agility
The Migration Plan
We didn’t dive into microservices overnight. Here’s how we approached it:
Step 1: Identify Bounded Contexts
- Separated User Management, Order Processing, and Inventory as clear domains.
Step 2: Create API Contracts
- Defined REST interfaces between services using OpenAPI
- Started writing consumer-driven contracts
Step 3: Incremental Extraction
- Moved Order Service into its own Spring Boot project
- Used Kafka for async events between services
- PostgreSQL per service, avoiding cross-service joins
Step 4: Introduce Docker & CI/CD
- Containerized each service
- Set up Jenkins pipelines for independent deployment
- Used Kubernetes (EKS) to manage service discovery and scaling
What We Learned
- Logging and Monitoring (Grafana + Prometheus) are non-negotiable
- Data consistency across services is challenging
- CI/CD pipelines need to mature with the architecture
- Don’t split services too early — focus on real pain points
The Results
- Deployment frequency: ⬆️ 5x increase
- Downtime: ⬇️ 90% reduction
- Team autonomy: ⬆️ Backend teams can now own services end-to-end
- Scalability: Services auto-scale based on load