A better heuristic is: whoever is the better organizational and people leader should be the STO.
Implementing Amazon’s single threaded owner model a retrospective | Jade Rubick - Engineering Leadership
A Single Threaded Owner (STO), is a single leader that is completely responsible for their area of the product. I share my experiences implementing this model, including the tradeoffs and challenges. And I give the nuts and bolts of how we implemented it and what we learned.
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