What is the difference between monolithic and microservices architecture in Node.js?

A monolithic architecture packages all application functionality (auth, billing, notifications, user management) as a single deployable unit running in one process. Simpler to develop, test, and deploy initially; easier to debug (single log stream, single codebase); no network overhead between components. Drawbacks: as the app grows, it becomes harder to scale specific bottlenecks (must scale everything), slower deployments, technology lock-in, and risk of tight coupling. A microservices architecture decomposes the application into small, independently deployable services, each responsible for a single business capability. Each service has its own codebase, database, and deployment pipeline. Benefits: independent scaling, technology diversity (mix Node.js, Python, Go), isolated failures, parallel team development. Drawbacks: network latency between services, distributed transaction complexity, operational overhead (container orchestration, service discovery, monitoring). For Node.js, frameworks like NestJS and tools like gRPC, RabbitMQ, Apache Kafka, and Docker/Kubernetes support microservices. Start monolithic — migrate to microservices when clear bottlenecks or team scaling demands it.