react developer freelancer for app refactoring and cleanup react automatic batching nextjs seo optimization mern stack development company hire full stack developer responsive web design freelancer for headless ecommerce sites react component-driven development react recoil state management jotai state management react query data fetching python web development react development https://myleszyacx.activablog.com/35539327/the-best-side-of-software-developer-kpi-template