Senior Full-Stack Developer Needed to Build V2 of an Existing SaaS Platform

I have an existing B2B SaaS platform and am looking for a senior full stack developer to build out Version 2. The platform has been live for a while, and fulfills basic business needs such as: customer login/signup, admin portal, Stripe payments, add to cart, place order, document uploads, etc. I am looking to upgrade the existing features, especially the admin portal to give admin users more flexibility such as order cancellation and handling disputes. I would also like to look into adding a FedEx API integration for orders. The existing stack is React/Next.js, TypeScript, Node.js, PostgreSQL, Stripe, and REST APIs, but I’m open to suggestions if you think parts of the existing architecture should be improved. Please make sure you’re comfortable with jumping onto an existing codebase. I am looking for someone who has experience working with established businesses, and can understand the entire business flow and make suggestions from the technical perspective. When applying, please send a few examples of some SaaS products you’ve worked on and what you personally did on them. Even better if you were tasked with solving a business problem with code. If things go well, I will likely need maintenance and potentially more new features developed in the future.