Microservices Communication: REST, gRPC, and Message Queues

The Communication Problem in Microservices When you split a monolith into services, every function call becomes a network call. Network calls fail. They're slow. They're asynchronous. Choosing the right communication pattern determines whether your microservices work together or fight each other. Three Patterns 1. Synchronous REST Service A calls Service B, waits for a response. // Order Service calls Inventory Service async function createOrder(items: OrderItem[]) { // Check inventory (synchronous call) const availability = await fetch('http://inventory-service/api/check', { method: 'POST', headers: { 'Content-Type': 'application/json' }, body: JSON.stringify({ items }), }).then(r => r.json()); if (!availability.allAvailable) { throw new Error('Some items are out of stock'); } // Create order... } Good for: Simple request-response. When you need the result immediately. Problem: If Inventory Service is down, Order Service is down too. Cascading failures. // Mitigation: circuit break