What are regions and availability zones in the cloud?
A region is a geographic area where a cloud provider has data centres, like a location in India or the US. Within a region there are availability zones, which are separate data centres that are isolated from each other. Spreading your app across zones means that if one zone fails, your app keeps running in another.
- A region is a geographic area containing multiple data centres.
- An availability zone is one or more isolated data centres within a region.
- Spreading across zones improves fault tolerance and availability.
Why they matter
- Region: pick one close to your users for lower latency.
- Availability zone: isolated data centre inside a region for fault tolerance.
- Using multiple zones protects against a single data centre failure.
If you run only in one zone and it loses power, your app goes down. By running across two or more zones, a failure in one zone does not take your whole service offline.
Mention high availability. Saying you deploy across multiple availability zones to stay up even if one data centre fails is exactly the reliability thinking interviewers look for.
Frequently asked questions
Why deploy across multiple availability zones?
If one zone fails due to a power or network issue, your app keeps running in the others, which greatly improves availability.
How do you choose a region?
Pick a region close to your users for lower latency, and also consider cost, compliance rules, and which services are available there.
Common follow up questions
Related interview questions
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