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 fa