What is the difference between rolling, blue-green, and canary deploys?
PICTURE THIS: STACK VS QUEUE
Simple meaning
Rolling replaces instances gradually on the same environment.
WHY — Deployment instead of guessing?
Why interviewers care about Deployment:
contrast on Deployment, not two memorised paragraphs.
the developer, then one case where picking wrong hurts.
Name the idea, why it exists, then one short example.
End with when you use it and one common pitfall.
STEPS — What happens step by step?
Before you speak the answer, walk the interviewer through these steps:
- 1Rolling replaces instances gradually
on the same environment.
- 2Blue-green keeps two full
stacks and switches traffic at the proxy.
- 3Canary sends a small
percentage of users to the new version first so you can abort with limited blast radius.
- 4Give an example
One tiny concrete case you can say aloud.
- 5Common mistake
What juniors usually get wrong.
- 6Close
When you pick this over the alternative.
EXAMPLE — See it in action
Here's a short line you can speak, broken into clear beats:
Note: Adapt this scaffold to your own project — keep it under 60–90 seconds.
Key takeaway
Rolling replaces instances gradually on the same environment. Blue-green keeps two full stacks and switches traffic at the proxy.