Keel: Keep Architecture's Load-Bearing Spine Small

Keel does not choose microservices, DDD or a framework. It governs the parts that decay: public contracts are expensive, cross-module interfaces come next, and module internals and wiring should stay cheap to change. Every boundary has one owner; every fact has one source, while caches and reports remain disposable projections. Designs must cover denial, failure, interruption, replay and recovery. Important rules become machine checks that can actually fail; exceptions are dated and shrink-only. Repeated bypasses signal that the governed route costs too much. A whole-system rewrite is reduced to the smallest rewritable slice, and every new concept should name something it will eventually retire.