Core Microservices Patterns

2.1 API Gateway Pattern

The API Gateway acts as a single entry point for all client requests and routes them to various microservices. It can also handle cross-cutting concerns such as authentication, logging, and rate limiting.

app.get('/api/serviceA', (req, res) => {
                    // Route to Service A
                });

2.2 Circuit Breaker Pattern

This pattern prevents a service from continually trying to execute an operation that's likely to fail. If a service fails more than a predefined threshold, the circuit breaker opens and further calls are failed immediately, allowing time for recovery.

if (circuitBreaker.isOpen()) {
                    // Handle failure
                } else {
                    // Call service
                }

2.3 Service Discovery Pattern

Service discovery enables services to find each other dynamically. This can be done via client-side discovery (where clients query a service registry) or server-side discovery (where a load balancer does the routing).

const serviceUrl = serviceRegistry.getService('serviceA');

2.4 Database per Service Pattern

Each microservice manages its own database. This ensures loose coupling and helps in scaling services independently. However, it complicates transactions across services.

2.5 Event Sourcing Pattern

This approach stores all changes to application state as a sequence of events. This allows you to reconstruct the current state of an application from its event history.

eventStore.save(event); // Save an event