An Availability Zone (AZ) is an isolated data center within a cloud region with its own power supply, cooling, and network connectivity. Cloud providers such as AWS, Azure, and GCP typically operate two to four AZs per region.
For an ISMS, Availability Zones are the operational foundation for ISO 27001 Annex A control A.8.14 (Redundancy of Information Processing Facilities). By distributing workloads across multiple AZs, you achieve high availability even if an entire data center fails. Latency between AZs within a region is typically under 2 ms, allowing synchronous replication. Document in your ISMS which systems are distributed across multiple AZs and which operate in a single AZ only.