Patterns

Reusable solutions at three altitudes. Keeping them separate matters - conflating a code idiom with an architectural decision is a category error.

• code/ - object/class level: GoF (strategy, factory, observer…), language idioms.
• architectural/ - system shape: CQRS, event sourcing, saga, strangler fig, hexagonal/ports-and-adapters, BFF.
• distributed/ - coordination under failure: outbox, idempotency keys, leader election, quorum, circuit breaker, bulkhead.

Each pattern note: problem → solution → when to use → when not to → real example.