Senior Full-Stack Developer — AI Integration, Supabase, Python & React

I'm looking for a senior full-stack developer to audit, stabilize, and complete an existing AI-integrated web application. This is an existing codebase, so you should be comfortable understanding unfamiliar code, identifying gaps, and making pragmatic improvements. The business domain, proprietary use case, datasets, and product objectives are confidential. An NDA is required before proprietary details, code, or data are shared. This public description intentionally focuses on technical requirements. INITIAL PAID TECHNICAL AUDIT — $200–$500 Review the existing architecture, code quality, database design, integrations, deployment setup, and testing. Identify what works, what is incomplete, key risks, and the highest-priority fixes. Deliver a concise written assessment and a practical completion plan with proposed milestones, estimates, and acceptance criteria. Further implementation will be agreed after the audit. IMPLEMENTATION SCOPE • Complete and improve backend and frontend workflows in the existing application. • Work with Supabase/PostgreSQL, Python, and React/Next.js. (not set in stone, open to discussion) • Implement or improve AI API integrations using OpenAI and/or Gemini, including structured outputs, validation, error handling, retries, and cost awareness. • Improve data pipelines and third-party API integrations, with reliable processing and clear error reporting. • Review authentication, access controls, secret handling, and database security. • Add appropriate tests, resolve bugs, and establish a reliable deployment process. • Provide clear documentation and a practical handover. IDEAL FIT An individual expert freelancer who can work across the stack, explain tradeoffs clearly, and take ownership of an existing application. Please show relevant examples of applications you have audited, completed, or maintained, particularly those combining a relational database, Python services, a React interface, and AI APIs. Domain-specific experience is not required. BUDGET & WORKING ARRANGEMENT Initial budget: $1,500–$3,000, including the $200–$500 paid technical audit. Fixed-price milestones with agreed deliverables and acceptance criteria. The $3,000 listing figure represents the upper end of the initial budget; final scope and milestone amounts will be agreed after the audit. Initial timeline is provisionally 1–2 months and will be refined following the audit. Worldwide applicants welcome. There may be ongoing maintenance and further development work following successful completion. PLEASE INCLUDE 1. Two relevant project examples and your specific role. 2. Your experience with Supabase/PostgreSQL (or equivalents), Python, React/Next.js, and OpenAI/Gemini APIs. 3. How you would approach the initial audit and what you would deliver. 4. Your availability and proposed hourly rate and estimated hours needed for the audit within the stated range. 5. Confirmation that you work as an individual freelancer and are comfortable signing an NDA before receiving proprietary details. Please share only examples you are authorized to disclose; confidential client code or datasets are not requested.