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Rolling vs Blue-Green vs Canary Deployments: Which Should You Pick?
Compare rolling, blue-green, and canary deployment strategies: downtime, rollback speed, cost, and complexity — with a decision table.
Quick answer
- Rolling updates replace instances a few at a time — the default, cheapest, and good enough for most apps.
- Blue-green switches all traffic between two full environments, giving instant rollback at double the cost.
- Canary shifts a small slice first, limiting blast radius but requiring real metric analysis.
The three strategies compared
| Attribute | Rolling | Blue-green | Canary |
|---|---|---|---|
| How it works | Replace instances gradually | Swap all traffic between two envs | Shift a small traffic slice first |
| Downtime | None (brief mixed versions) | None | None |
| Rollback speed | Moderate (reverse the rollout) | Instant (re-route) | Fast (re-route the slice) |
| Blast radius of a bad release | Growing during rollout | All users at once | Small slice first |
| Cost | No extra environment | ~2x during switch | Slightly higher |
| Complexity | Low | Medium | Medium–high |
When to choose each
Choose rolling for the vast majority of apps: it is simple, cheap, and built into most platforms as the default. Choose blue-green when instant rollback matters more than cost, or when you want to test in a production-shaped environment before switching. Choose canary when you have high traffic, real-time metrics, and a need to catch issues that only real users trigger — the standard for large or revenue-critical services.
How to decide
Start from blast radius and rollback. If a bad release must affect as few users as possible, canary. If rollback must be one action, blue-green. If neither is critical, rolling. Many teams combine ideas: rolling for routine changes, canary for risky ones.
Where this bites vibecoders
AI assistants default to the simplest thing — often a raw restart or a full replace — without asking about your rollback story. The real question before any deploy is “how do I undo this in one step, and how many users are affected while I find out?” Pick a strategy because it answers that question, not because it’s the default in the generated script.
Where AI coding assistants get this wrong
- Deploying by
kubectl delete && apply, causing downtime that any of the three strategies would avoid. - Calling a config “blue-green” without actually provisioning a second environment.
- Choosing canary without any metric comparison, so the “canary” is just a slow full deploy.
- Omitting rollback steps from the generated runbook.
Checklist
- Decide rollback and blast-radius requirements before choosing a strategy.
- Use rolling as the default for ordinary services.
- Reach for canary for high-traffic or revenue-critical services with metrics.
- Use blue-green when instant rollback is non-negotiable.
- Document and rehearse the rollback for whichever strategy you pick.
FAQ
Which strategy is the default in Kubernetes?
Kubernetes Deployments use a rolling update by default: pods are replaced gradually according to maxSurge and maxUnavailable. Blue-green and canary require extra tooling or manual traffic control. See What Is Kubernetes?.
Does rolling deployment cause downtime?
A correctly configured rolling update has no downtime, but during the rollout both old and new versions serve traffic simultaneously. That means old and new code must be compatible with each other and with the shared data.
Can I combine these strategies?
Yes. Canary into a blue-green environment, or rolling within a canary stage, are common hybrids. The goal is always the same: bound the damage of a bad release and make rollback cheap.