# Choose availability across zones and regions

Taiga Learning · Worksheet
https://taiga.training/en/lessons/high-availability/

Use fictional or approved information. Do not put secrets in this worksheet.

## Learning objectives
- Explain the difference between an Availability Zone and a Region.
- Find shared dependencies that defeat an availability design.
- Compare the business value and operating cost of multi-region deployment.

## Exercise
A fictional booking service runs web replicas in two AZs. Its database and outbound gateway occupy one AZ. Draw the request path. Remove that AZ on paper. Identify what still works, what fails, and which test would verify your conclusion.

## Your response
- Scenario and scope:
- Assumptions and open questions:
- Proposed answer or decision, with reasons:

## Verify your response
| Claim or criterion | Evidence or test | Result or gap | Owner |
| --- | --- | --- | --- |
| | | | |
| | | | |
| | | | |

## Next action
- Action, owner, and date:
- When will you review this response?

## Principle to retain
Availability depends on the complete service path. Choose fault boundaries and capacity for a defined failure scenario, then test them.

## Sources
- [AWS: Deploy the workload to multiple locations](https://docs.aws.amazon.com/wellarchitected/latest/reliability-pillar/rel_fault_isolation_multiaz_region_system.html)
- [AWS: Shared responsibility model for resiliency](https://docs.aws.amazon.com/wellarchitected/latest/reliability-pillar/shared-responsibility-model-for-resiliency.html)
- [Google SRE: Implementing SLOs](https://sre.google/workbook/implementing-slos/)

This worksheet supports learning. Completing it does not itself authorize a production change.