AWS global infrastructure hierarchy explained: Region, Availability Zone (AZ), and data center.
Why This Structure Exists
AWS separates infrastructure into Region -> AZ -> data center to solve concrete architecture problems:
- Fault isolation: AZs are isolated from each other, so one-site failures do not take down the full Region.
- High availability: You can run active workloads across multiple AZs with low latency.
- Data residency and governance: You choose Region based on legal, regulatory, and business requirements.
- Disaster recovery design: You can do multi-AZ (within a Region) and multi-Region (across Regions) patterns intentionally.
- Operational scale: AWS can grow capacity by adding AZs and data centers without changing customer architecture patterns.
Core Definitions (Short)
- A Region is a separate geographic area that contains multiple AZs.
- An Availability Zone (AZ) belongs to one Region and is an isolated fault boundary.
- An AZ consists of one or more physical data centers.
Hierarchy
AWS Global Infrastructure
-> Region (for example us-east-1)
-> Availability Zone (for example us-east-1a)
-> One or more physical data centersCurrent AWS Scale (As of February 8, 2026)
From the official AWS Global Infrastructure page:
- 39 launched geographic Regions
- 123 Availability Zones
- Announced: 2 more Regions and 7 more AZs (Saudi Arabia and Chile)
These numbers change as AWS launches new infrastructure. Re-check the official page before using in production docs or exams.
How Many AZs Per Region?
- AWS documentation states each Region has at least three AZs.
- The exact AZ count varies by Region.
Design Implications
- Single-AZ design: Lowest cost, lowest resilience.
- Multi-AZ design: Standard production baseline for high availability in one Region.
- Multi-Region design: Higher complexity/cost, used for regional disaster recovery and strict continuity targets.
Examples
us-east-1= Regionus-east-1a,us-east-1b,us-east-1c= AZ names within that Region- Each of those AZs maps to one or more physical data centers
Resources
AWS Global Infrastructure
Official count of Regions, AZs, and announced expansions.Regions and Availability Zones
Official AWS documentation for Region and AZ concepts.AWS Fault Isolation Boundaries - Availability Zones
Official definition of AZs as one or more discrete data centers.