Two-Pizza Team
Amazon's heuristic that a team should be small enough to be fed by two pizzas, and — the substantive part — should own its service end to end.
The size heuristic gets quoted; the operating model is what mattered. The teams were autonomous and accountable end to end: they owned their service's roadmap, its code, its deployment, its operation and its on-call — "you build it, you run it".
The architectural consequence is the one relevant to an architect. Autonomy at that granularity requires services that can be developed and released independently, which requires clean boundaries and API-only communication between them. Amazon's well-known internal mandate that all teams expose functionality through service interfaces, with no other form of integration permitted, is the structural enforcement of exactly this — and is generally credited as a precondition for what became AWS.
The lesson to take is not the pizza count. It is that team autonomy and service boundaries are the same decision, and that granting the former without designing the latter produces teams that are accountable for outcomes they cannot control alone.