Monolith vs Microservices: When to break it apart

The Monolith

What it is: One big codebase. One database. One deployment artifact.

• Pros: Simple to develop, test, and deploy. IDE navigation is instant. ACID transactions are easy in a single DB.
• Cons: Hard to scale teams. If 50 developers work on one repo, merge conflicts are constant. A memory leak in one module crashes the whole site.

Microservices

What it is: Breaking the app into small, independent services (User Service, Order Service, Billing Service), communicating via APIs.

• Pros: Independent scaling (scale the Billing service without scaling the User service). Technology freedom (write Billing in Java, User service in Node).
• Cons: Distributed Complexity. You trade code complexity for network complexity. You now need service discovery, distributed tracing, circuit breakers, and eventual consistency.

The "Strangler Fig" Pattern

Don't rewrite a monolith from scratch. Instead, peel off one feature at a time (e.g., "Search") and turn it into a microservice. Route traffic for "Search" to the new service while keeping the rest on the Monolith. Repeat until the Monolith is gone.

Key Takeaway

Start with a Monolith. Break it apart only when your organization structure demands it. Microservices solve people problems (scaling teams), not technical problems.