What is the difference between message queue and event bus?

Question

Accepted Answer

**Message Queue** — point-to-point communication. **Event Bus** — publish-subscribe communication.

**Message Queue:**
- One consumer per message.
- Point-to-point.
- Guaranteed delivery.
- Work distribution.

```
Message Queue:
Producer → [Queue] → Consumer 1
                  → Consumer 2
(Message consumed by one)
```

**Event Bus:**
- Multiple subscribers.
- Publish-subscribe.
- Fan-out.
- Event distribution.

```
Event Bus:
Publisher → [Bus] → Subscriber 1
                   → Subscriber 2
                   → Subscriber 3
(Event received by all)
```

**Key differences:**
- **Queue** — one consumer.
- **Bus** — many subscribers.
- **Queue** — work distribution.
- **Bus** — event distribution.

Systems Analyst: What is the difference between message queue and event bus?