AWS, Azure & GCP · Cloud across providers
What are regions and availability zones?
Short answer
A region is a geographic area containing multiple isolated availability zones. AZs are separate data-centre groups with independent power and networking, so you deploy across them to survive a single-zone failure.
Regions let you place workloads close to users and satisfy data residency requirements. Within a region, availability zones are independent failure domains connected by low-latency links. A single AZ can fail without taking the others down.
Choosing placement
- Region choice: latency to users, legal residency, service availability, price and disaster recovery distance
- Multi-AZ: the default for production stateless tiers and replicated databases
- Multi-region: for region-level failure, global latency or strict residency, at higher cost and complexity
- Zone names are not stable across accounts; use zone IDs when you need consistent physical mapping
aws ec2 describe-availability-zones --region ap-south-1 --query "AvailabilityZones[].ZoneName"Spreading instances across AZs only helps if the dependency chain is also spread. A load balancer, database and cache all need zone-aware configuration, or the surviving zone still depends on a failed component.
Follow-ups you should expect
Interviewers use these to check whether the first answer was understanding or memorisation.
- 1How do you choose a region for a new workload?
- 2Why are AZ names not reliable across AWS accounts?
- 3What dependencies must also be zone-aware for multi-AZ to help?
- 4When is multi-region justified over multi-AZ?
Say it in the interview
A region is a geographic area, and within it availability zones are isolated data-centre groups with independent power and networking. I deploy production tiers across at least two AZs so one zone failure does not take the service down. I choose the region for latency, residency, service availability and cost, and I remember that multi-AZ is resilience, not a backup strategy.
Use this as a model, not a script. Saying it in your own words is what makes it survive follow-up pressure.
Related questions
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