Full-Stack Developer Needed to Audit, Complete & Launch Existing Web, iOS & Android App

Experienced Full-Stack Developer / Small Team Needed — Complete, Secure & Launch Existing Web, iOS and Android Application We are a UK-based company seeking an experienced, reliable full-stack developer or small development team to review, complete, secure, test and launch an existing software application. IMPORTANT: This is an existing project with a substantial codebase and implemented functionality. We are NOT looking for a complete rebuild or a new application developed from scratch. Project Overview The application has been developed using a modern React and TypeScript stack, with Supabase/PostgreSQL for backend services. We are looking for a professional who can take responsibility for the remaining technical work and deliver a secure, stable, production-ready application across web, iOS and Android. Main Responsibilities 1. Technical Audit and Security - Review the existing codebase, architecture and database. - Identify and resolve bugs, security vulnerabilities and performance issues. - Review authentication, authorisation, database access controls and data privacy. - Implement appropriate security improvements and reliable error handling. 2. Application Completion - Verify existing features and workflows. - Resolve incomplete or malfunctioning functionality. - Improve reliability, performance and responsiveness. - Preserve the existing design, functionality and approved project structure. 3. Third-Party Integrations - Complete and verify payment and subscription integrations. - Configure professional transactional email and notifications. - Connect and verify production domain and hosting configurations. - Ensure integrations work securely and reliably. 4. iOS and Android Applications - Prepare production-ready mobile applications using an appropriate technical approach. - Test functionality on real iOS and Android devices. - Address applicable app-store requirements and payment policies. - Prepare and submit applications to the Apple App Store and Google Play Store. - Support the review and approval processes. 5. Testing and Launch - Conduct comprehensive functional, security and integration testing. - Fix issues identified during testing. - Prepare the production deployment. - Coordinate the web, iOS and Android public launch. - Provide technical documentation, source-code handover and post-launch support. Required Experience We are particularly interested in developers with proven experience in: - React, TypeScript and full-stack application development. - Supabase, PostgreSQL and secure backend architecture. - Stripe or equivalent payment integrations. - iOS and Android development and successful app-store submissions. - Application security, privacy and testing. - Working with and improving existing codebases. Project Expectations - Work with the existing application rather than unnecessarily rebuilding it. - Communicate clearly and provide regular progress updates. - Follow secure development practices. - Work under agreed milestones with measurable deliverables. - Respect project confidentiality and intellectual property ownership. - Provide a realistic timeline and transparent pricing. We prefer a fixed-price agreement divided into milestones. Our target is a coordinated web, iOS and Android launch, with the final timeline determined following technical assessment. When Applying, Please Answer: 1. Have you completed and launched an existing application developed by another developer or platform? 2. What experience do you have with React, TypeScript, Supabase and PostgreSQL? 3. Have you personally published applications to both the Apple App Store and Google Play? Please provide examples. 4. How would you approach auditing and securing an existing application before launch? 5. Do you have experience integrating payments, subscriptions, email and notifications? 6. Would you undertake this as an individual developer or as part of a team? 7. What is your availability, estimated timeline and preferred pricing structure? A more detailed project scope and technical information will be shared privately with suitable shortlisted candidates, subject to appropriate confidentiality arrangements. We are looking for an experienced and reliable professional who can take full responsibility for completing the agreed technical tasks, delivering the application to production-ready standards, and providing ongoing technical support when required. The client will retain exclusive ownership and control of the application, source code, intellectual property, brand, accounts and all project assets. The freelancer will have no ownership or equity interest in the application or company. All commissioned deliverables must be assigned to the client under the agreed contract.