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Optimal Lab

DevOps · interactive

Regions and availability zones

A cloud region is a metro area; inside it, availability zones are separate data centres with their own power and network, a few milliseconds apart. Where you place copies decides which failures you ride out.

eu-west-1 (Ireland)

zone a
zone b
zone c

A data center (zone) loses power: still serving

Cost ~1.1× (+ cross-zone traffic) · latency +~1 ms between zones

Yes. Multi-zone is the sweet spot for most apps: cheap and covers the common failures.

Deployment

Failure

Step 2 of 4

  1. 1

    Zones: separate buildings, same city

    Independent power and cooling, connected by fast links. Most managed services already span zones.

    Zone names differ per account.

  2. 2

    Spread across at least two zones

    Run instances in several zones behind a load balancer, with a multi-AZ database.

    Cross-zone traffic is billed: keep chatty services together.

  3. 3

    Regions for disaster recovery or latency

    A second region protects against regional outages and serves far-away users faster, at real cost and complexity.

    See failover and DR.

  4. 4

    Data residency

    Laws may require data to stay in a country or region. Pick regions for compliance as well as resilience.

    GDPR, data localisation rules.

In production

Tools and technologies

Every cloud is organised into regions and zones.

Not tied to one language — use these names when you search docs or design a system.