What is Availability Zone?
Also known as: AZ
An Availability Zone is an isolated, fault-tolerant data centre within a cloud region, with independent power, cooling, and networking to prevent single points of failure.
An Availability Zone (AZ) is a distinct, physically separate location within a cloud provider's region. Each AZ contains one or more data centres with their own redundant power supply, cooling equipment, and network connectivity. The key property is that AZs are engineered to be independent of each other: a failure in one AZ (caused by a natural disaster, power outage, or cooling loss) does not affect the others in the same region.
Cloud providers such as AWS, Google Cloud, and Azure offer multiple AZs per region (typically 2 to 6). Instances or services deployed in one AZ are isolated from failures in another AZ. To build a fault-tolerant application, you distribute workloads across at least two AZs. The AZs themselves are connected by low-latency, high-bandwidth links (often private fibre), allowing synchronous replication and traffic load balancing between them.
An AZ is the fundamental building block for high availability in cloud architecture. It sits between the region (a geographic area containing multiple AZs) and the individual VM or container instance. Understanding AZ boundaries is critical for designing systems that survive infrastructure failures without data loss or downtime.
Key facts
- Each AZ is a physically separate facility with independent power, cooling, and network.
- Cloud regions contain 2 to 6 Availability Zones (e.g., AWS us-east-1 has 6 AZs).
- AZs are connected via low-latency private fibre for synchronous replication.
- Distributing workloads across 2+ AZs protects against single-point-of-failure outages.
- Traffic between AZs incurs standard data transfer costs in most cloud providers.
How it works in practice
Related terms
References
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