QPNotes is a SaaS platform I built and led as Technical Lead, designed to help individuals, teams, and organizations manage and use AI prompts more efficiently. I developed the full backend architecture using Python/Django, PostgreSQL, and Redis, with integrated AI capabilities powered by OpenAI, Claude, Gemini, and Groq. Users can create structured prompt libraries, chat with AI assistants using Retrieval-Augmented Generation (RAG), and track token usage via a custom billing engine. Key features: – Custom AI chat assistants with user/group/org settings – RAG pipelines using pgvector and PostgreSQL – Token billing system across users and organizations – Background task processing (Celery) for file parsing, transcription, and embedding – Permissions, sharing, and collaboration on prompt assets – Admin dashboards and API integrations This project blends deep backend logic with real-time AI integrations and a strong focus on performance, security, and usability.