What is a Microservice? Instead of building one big app that does everything, you split it into small independent services. Each service does one job and runs separately. I have two services: product-service - manages products (port 8081) order-service - manages orders (port 8082) These two services live in separate Spring Boot apps with separate databases. But when a customer places an order, order-service needs to know about the product — so they need to talk to each other . The Problem Order-service doesn't have product data. It only knows the productId from the request. So before saving an order it needs to ask product-service: "Hey, does this product exist? How much stock do you have?" The Solution - WebClient WebClient is Spring's HTTP client that lets one service call another service's REST API. Step 1 - Configure WebClient as a Bean @Configuration public class WebClientConfig { @Bean public WebClient productWebClient () { return WebClient . builder () .…