| # | Principle | One-Line |
|---|---|---|
| P1 | Abstraction | Hide irrelevant complexity |
| P2 | Modularity | Independent units |
| P3 | Composability | Small pieces combine cleanly |
| P4 | Separation of Concerns | One responsibility per component |
| P5 | Idempotency | Same operation twice = same result as once |
| P6 | Reproducibility | Same input → same output, every time |
| P7 | Immutability | Data does not change; new versions are created |
| P8 | Locality | Data and compute live close together |
| P9 | Fault Tolerance | Continues operating when components fail |
| P10 | Observability | You can tell what the system is doing from outside |
| P11 | Consistency | Same conditions produce same behaviour |
| P12 | Security Boundaries | Trust is verified, not assumed |
| P13 | Fail Fast | Detect errors early; stop rather than propagate |
| P14 | Least Privilege | Only the access needed, no more |
| P15 | Measure & Adapt | Improve empirically, not by assumption |
Use: As a checklist before deployment. Each absent principle predicts a failure mode.