Product lead. Owns the goal and the backlog. Says no to scope that does not serve the goal. Your single point of contact.
Engineers. Frontend, backend and mobile. They write the code and they explain the trade-offs in plain words.
Designer. Flows, screens and the design system. Works ahead of the build, never behind it.
QA. Tests every release. Writes the checks that stop the same bug twice. See QA and testing.
Performance marketer. Runs paid channels against pipeline, not clicks.
SEO and content. Makes the product findable and writes copy that a buyer believes. See technical SEO.
Analytics. Owns the event plan and the dashboards. Nothing ships untracked.