Comprehensive App Backend Development

I need a production-ready backend that covers three core pillars: user authentication and management, robust database handling, and versatile API connectivity. The data layer must run on PostgreSQL, so your solution should take advantage of its relational strengths, indexing, and security features... (Budget: $30 - $250 USD, Jobs: API Development, Backend Development, Django, FastAPI, Node.js, NoSQL Couch & Mongo, PostgreSQL, Python)