What is the difference between event-driven and request-driven architecture?

Question

Accepted Answer

**Request-Driven** — client initiates. **Event-Driven** — events trigger.

**Request-Driven:**
- Client sends request.
- Server responds.
- Synchronous.
- REST, GraphQL.

```
Request-Driven:
Client → Request → Server → Response
(Client initiates, waits)
```

**Event-Driven:**
- Events trigger actions.
- Decoupled services.
- Asynchronous.
- Kafka, RabbitMQ.

```
Event-Driven:
Service A → Event → Bus → Service B
                        → Service C
(Event triggers multiple)
```

**Key differences:**
- **Request** — client-initiated.
- **Event** — event-triggered.
- **Request** — synchronous.
- **Event** — asynchronous.

Systems Analyst: What is the difference between event-driven and request-driven architecture?