How do you scale Scrum across multiple teams?

Scaling Scrum requires coordination mechanisms beyond single-team Scrum. Approaches: (1) Scrum of Scrums (SoS) — representatives from each team (typically Scrum Masters or technical leads) meet 2-3x/week to coordinate, remove cross-team impediments, and manage dependencies. Not a reporting ceremony — a collaborative coordination. (2) Nexus — the official Scrum Guide extension for scaling (3–9 teams). Adds a Nexus Integration Team (NIT), a shared Sprint Backlog, and Nexus-level events that wrap individual team events. (3) LeSS (Large Scale Scrum) — minimal roles and rules; uses feature teams (end-to-end capability teams), one Product Backlog, one Product Owner, multi-team Sprint Planning and Retrospectives. (4) SAFe — adds Program Increment Planning (PI Planning) quarterly events, Release Train Engineers, and a layered hierarchy. (5) Shared Definition of Done — all teams must agree on and meet a shared DoD for integrated increments. Key challenge in all approaches: feature teams (preferred over component teams) reduce coordination overhead by enabling end-to-end delivery without cross-team handoffs.