Microservices vs Monolith: API Design Implications
The choice between monolithic and microservices architecture has direct implications for how APIs are designed, versioned, and consumed. Understanding these trade-offs helps you make informed architectural decisions for your project's stage and scale.
Monolithic Architecture
A monolith packages all application functionality in a single deployable unit. APIs in a monolith are typically internal function calls rather than HTTP requests — fast, simple, and easy to change. The monolith exposes one external API surface.
Monolith advantages: simpler deployment, easier debugging, simpler transactions, no network latency on internal calls. Disadvantages: as the codebase grows, modules become tightly coupled; the entire application must be deployed for any change; scaling requires scaling everything.
Microservices Architecture
Microservices divide application functionality into independently deployable services communicating via APIs (typically HTTP or message queues). Each service has a well-defined API that other services consume.
Microservices advantages: services can be developed, deployed, and scaled independently; teams can own services; different services can use different technology stacks. Disadvantages: distributed systems complexity (network calls, service discovery, eventual consistency), operational overhead (many services to monitor and deploy), harder to change data models that span services.
The Recommended Path
Start with a well-structured monolith. Extract services when: specific services need to scale independently, teams are blocked by coupling, specific parts require different deployment cadences. The "strangler fig" pattern gradually extracts services without a big-bang rewrite. Microservices are often premature optimisation for early-stage products.