Glossary
Operational
| Characteristic |
Definition |
| Availability |
Percentage of time the system is accessible and functional |
| Continuity |
Business operations continue during disasters (disaster recovery, backups) |
| Performance |
Response times, throughput, and resource efficiency |
| Recoverability |
How quickly the system recovers from failures (RTO/RPO) |
| Reliability |
Ability to function correctly over time, handle errors gracefully |
| Robustness |
Ability to handle unexpected inputs or conditions without crashing |
| Scalability |
How well the system handles increased load (vertical or horizontal) |
Structural
| Characteristic |
Definition |
| Configurability |
Behavior changes through configuration rather than code changes |
| Deployability |
How easily and safely the system can be deployed to production |
| Extensibility |
How easily new functionality can be added |
| Maintainability |
How easily developers can understand, debug, and modify the code |
| Portability |
How easily the system moves between environments, platforms, or cloud providers |
| Testability |
How easily the system can be tested, including automated verification |
| Upgradeability |
How easily the system adopts new versions of dependencies or infrastructure |
Cloud-Specific
| Characteristic |
Definition |
| On-Demand Scalability |
Scales resources based on actual load rather than predicted peak capacity |
| On-Demand Elasticity |
Automatically scales up and down, minimizing cost during low demand |
| Zone-Based Availability |
Distributed across availability zones to survive zone-level failures |
| Region-Based Privacy |
Data residency restricted to specific geographic regions |
Cross-Cutting
| Characteristic |
Definition |
| Accessibility |
Usable by people with disabilities |
| Authentication |
Verifies user identity |
| Authorization |
Controls what authenticated users can do |
| Legal |
Meets regulatory compliance requirements |
| Privacy |
Protects user data from unauthorized access and use |
| Security |
Protects the system from malicious actors and vulnerabilities |
| Supportability |
How easily support teams can diagnose and resolve issues |
How to Measure
| Characteristic |
Metrics |
| Performance |
Response time, throughput, latency (percentiles matter more than averages) |
| Availability |
Uptime percentage, mean time between failures (MTBF), mean time to recovery (MTTR) |
| Scalability |
Maximum throughput, concurrent users supported, resource utilization under load |
| Reliability |
Error rates, successful transaction percentage, data integrity metrics |
| Maintainability |
Cyclomatic complexity (target: <5, acceptable: <10), lines per method, dependency depth |
| Extensibility |
Number of extension points, plugin API coverage, customization without core changes |
| Testability |
Test coverage percentage, test execution time, ease of creating test fixtures |
| Deployability |
Deployment frequency, deployment duration, rollback success rate |
| Supportability |
Mean time to diagnose issues, resolution time, number of escalations |
