Availability Zone
Definition
An Availability Zone (AZ) is one or more discrete data centers with redundant power, networking, and connectivity in a cloud provider's region. AZs are physically separate from each other, by a meaningful distance, to protect against local failures like fires or floods.
Why It Matters
AZs are the fundamental building block for creating highly available applications in the cloud. By deploying your application across multiple AZs within a region, you can ensure that it remains operational even if one entire data center fails.
Contextual Example
A user runs their primary database in AZ `us-east-1a` and maintains a synchronous replica in AZ `us-east-1b`. If the data center in `us-east-1a` fails, the application can instantly failover to the replica in `us-east-1b` with no data loss.
Common Misunderstandings
- A region is a collection of AZs.
- The latency between AZs in the same region is very low (typically under 2ms).