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Microservices with Spring Cloud Study Material
What are Microservices
What are Microservices?
A microservice architecture builds one application as a set of small, independent services. Each service does one business job, runs in its own process, owns its own data, and talks to other services over the network (usually HTTP/JSON or messages).
- Small and focused: one service = one business capability (products, orders, payments...).
- Independently deployable: you can release the Order service without touching the Product service.
- Owns its data: each service has its own database; no other service reads its tables directly.
- Talks over the network: REST calls, gRPC, or events through Kafka/RabbitMQ.
- Owned by one team: the team that builds it also runs it ("you build it, you run it").
A Simple Picture
Instead of one big application, ShopEase becomes several small applications. The browser or mobile app talks to them (later through an API Gateway):
React / Android app
|
+-------------+--------------+
| | |
v v v
+---------+ +-----------+ +-----------+
| Product | | Order | | User |
| Service | | Service | | Service |
| :8081 | | :8082 | | :8083 |
+----+----+ +-----+-----+ +-----+-----+
| | |
product_db order_db user_dbKey Words You Will Hear
| Term | Meaning |
|---|---|
| Service | A small, independently running application with one business job |
| Instance | One running copy of a service; a service can have many instances |
| API contract | The agreed request/response format a service exposes |
| Service discovery | How a service finds the address of another service (medium level) |
| API Gateway | The single entry point that routes outside requests to services (medium level) |
| Distributed system | A system whose parts run on different machines and talk over a network |
Note: Microservices is an architecture style, not a library. Spring Boot builds each service; Spring Cloud adds the tools that make many services work together.