What is the difference between blue-green and canary deployment?

Question

Accepted Answer

**Blue-Green** — two identical environments. **Canary** — gradual rollout.

**Blue-Green Deployment:**
- Two identical environments.
- Blue = current, Green = new.
- Switch traffic instantly.
- Easy rollback.

```
Blue-Green:
Before: [Blue (v1)] ← Traffic
        [Green (v2)]
After:  [Blue (v1)]
        [Green (v2)] ← Traffic
(Instant switch)
```

**Canary Deployment:**
- Gradual rollout.
- Small percentage first.
- Monitor for issues.
- Increase gradually.

```
Canary:
1. Deploy to 5% of users
2. Monitor metrics
3. If OK → 25% → 50% → 100%
4. If issues → rollback
(Gradual rollout)
```

**Key differences:**
- **Blue-Green** — instant switch.
- **Canary** — gradual rollout.
- **Blue-Green** — more resources.
- **Canary** — less resources.

Systems Analyst: What is the difference between blue-green and canary deployment?