How did microservices communicate with each other?

Microservices typically communicate with each other through network protocols, most commonly using HTTP/REST API or gRPC for synchronous interactions. Asynchronous message exchange mechanisms via message brokers such as RabbitMQ, Kafka, or ActiveMQ are also widely used, which helps improve system fault tolerance and scalability.

Example of a synchronous REST API call:

GET /user/123 HTTP/1.1
Host: user-service

Example of asynchronous message exchange via a message queue:

• Service A publishes an event to a Kafka queue
• Service B subscribes to this queue and processes the event

The choice of communication method depends on requirements for latency, reliability, and interaction complexity.