Overview
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Design
Architecture vs Design
Design Challenges
Design Goals
Concepts
Standards Based Design
Data Standards
Design Patterns
Clinical Serialization Standards
Security Standards
Serialization Standards
Terminology Standards
Transport Standards
Stereographic Projection
Event-Driven Design
Cultural-Dependent Design
Service Interface Design
Contract-Based Design
Distributed Transaction Design
Testability Design
Code Generation Design
Science of Great User Experiences
Visual Design
Glossary

Availability

Availability is a Metric that indicates how much of the time a system is available. It is typically expressed in a number of Nines.

Availability can be improved by deploying multiple instances:

within one Availability Zone,
across Availability Zones,
across Regions,
or even across CSPs.

Availability of #4 is better than #1, at the cost of Complexity, Cost, and Performance.