A small engineering team can ship remarkably well. The coordination overhead is low, decisions happen quickly, and everyone can hold the system in their head. That advantage does not persist automatically. We have watched teams of eight that moved faster than teams of eighty, and teams of eight that had somehow manufactured all the coordination problems of teams of eighty without any of the benefits. The difference is the operating model. Not the technology stack, not the deployment tooling, not the project management software. The practices that govern how work is owned, reviewed, shipped, supported, and learned from. These practices scale cleanly from five to fifteen engineers. Past fifteen, they almost always need to change. This article is about what works in the five-to-fifteen range, and the signs that a team has grown past it. Ownership: primary owners, not teams Every service, every major module, every integration should have a primary owner. A named engineer, not a team.…