What is the difference between eventual consistency and strong consistency?

Question

Accepted Answer

**Eventual Consistency** — data converges eventually. **Strong Consistency** — data always current.

**Eventual Consistency:**
- Data updates propagate.
- Reads may be stale.
- Higher availability.
- Better performance.

```
Eventual Consistency:
Write to Node A → Replicate
Read from Node B: may see old data
Eventually: all nodes converge
(Data converges)
```

**Strong Consistency:**
- Reads always latest.
- Lower availability.
- Higher latency.
- Critical operations.

```
Strong Consistency:
Write to Node A → Wait for confirmation
Read from any node: always latest
(Always current)
```

**Key differences:**
- **Eventual** — converges.
- **Strong** — always current.
- **Eventual** — available.
- **Strong** — consistent.

Systems Analyst: What is the difference between eventual consistency and strong consistency?