Add OpenAI / Claude AI Integration to Existing Node.js Web App and Deploy

We have a stable Node.js and React web application already running in production. We want to add an AI-powered feature on top of the existing platform. The core application and data model are already established. We are not looking to rebuild the product. We need an experienced developer who can integrate AI naturally into the existing architecture without disrupting current functionality. What We Need Built The exact feature will be confirmed before development. It may include: • AI chatbot / conversational interface using OpenAI or Claude over our existing application data • RAG pipeline with semantic search across existing records • AI-powered content generation using our application data as context • Automated summarization and classification of incoming records Technical Requirements Whatever solution is implemented, it must: • Support streaming LLM responses correctly from the Node.js backend through to the React client • Handle model timeouts, API failures, and rate limits gracefully without breaking the user experience • Include token usage tracking and cost controls to keep AI usage within budget • Keep AI functionality cleanly separated from existing business logic • Follow production-quality security and error-handling practices • Be deployed to our existing infrastructure, including environment configuration and deployment setup Existing Stack Frontend • React • TypeScript • Tailwind CSS Backend • Node.js • Express • TypeScript Database • MongoDB Atlas Authentication • JWT Infrastructure • AWS / VPS • Nginx • Vercel where applicable What We're Looking For You should have: • Experience integrating OpenAI or Claude APIs into production applications • Strong Node.js and Express experience with existing production codebases • Experience implementing streaming LLM responses in production applications • Experience with RAG, embeddings, semantic search, or similar AI patterns • Experience deploying Node.js applications to AWS, VPS, or similar infrastructure • Ability to work within an existing architecture without unnecessary rewrites • Strong understanding of production concerns such as reliability, security, latency, and AI cost management To Apply Please share: • A brief overview of your relevant experience • Examples of relevant AI integration work • Which AI technologies you have used (OpenAI, Claude, RAG, vector databases, etc.) • Your availability and estimated timeline We are looking for a developer who can integrate AI into an existing production application cleanly, reliably, and with a strong focus on maintainability and performance.