How to Answer: "How do you approach microservices decomposition from a monolith?"

“Decomposing a monolith should be driven by business domain boundaries and scaling needs, not trendy architecture. I start by applying Domain-Driven Design to establish bounded contexts. I employ the Strangler Fig pattern, routing traffic via an API Gateway (like Envoy or Kong) to route specific endpoints to the new microservice while fallback goes to the monolith. For data migration, I isolate tables first within the monolith schema before splitting into separate databases, using event-driven CDC (like Debezium) or dual-writes during transition. Distributed tracing (OpenTelemetry) and resilience patterns like circuit breakers are established from day one.”

“I approach decomposition incrementally using the Strangler Fig pattern. First, I locate clear service boundaries like authentication or notifications that have minimal database coupling. I build the microservice alongside the monolith, route a small percentage of traffic using an API gateway, and verify parity before completely deprecating the monolith path.”

“I would start by identifying loosely coupled modules in the codebase. Then, behind an API gateway, we can extract one module at a time into an independent service, ensuring comprehensive integration testing so existing monolith functionality remains uninterrupted.”