The twelve models are not independent. Several pairs create productive tension:
MM5 (State) constrains MM9 (Redundancy): Adding redundant copies creates the question of which copy is current. Redundancy is never free — it converts a single-component problem into a consistency problem.
MM7 (Feedback) amplifies MM8 (Concurrency): Under concurrency, feedback loops can amplify problems faster than any single-threaded system. The thundering herd and retry storms are feedback effects that concurrency makes worse.
MM11 (Indirection) enables MM10 (Layered Abstraction): Every abstraction layer is built from indirection — a stable interface that hides the implementation below. The two models are inseparable in practice.
MM12 (Tradeoffs) governs all others: Which lens to apply is itself a tradeoff decision. Fluency is not knowing all twelve individually — it is knowing when to switch between them.
Apply the models in sets: diagnosing a slow system needs MM4 (Flow) + MM3 (Optimisation) + MM7 (Feedback). Diagnosing a consistency failure needs MM5 (State) + MM8 (Concurrency) + MM9 (Redundancy). No single model covers the whole system.