Senior Full-Stack Developer for Real-Time Darts Scoring App Rebuild

Black Country Arrows (BCA) is a growing UK grassroots darts organisation. We currently have a live application built using Base44 that includes player profiles, rankings, memberships, leagues, event management and live darts scoring. The app has proven there is demand, but live use has exposed reliability, performance and data-integrity problems. We are now looking for a senior full-stack product engineer to help us safely extract what we own from Base44 and begin creating an independently owned, reliable BCA platform. This is not a request to rebuild the entire platform in one contract. The first engagement will consist of a short paid technical discovery followed by a tightly scoped, production-quality vertical slice of our scorer. CURRENT POSITION • BCA currently runs a 53-event darts circuit. • Venue tournaments are being protected through Dart Atlas while our own technology is rebuilt. • Our existing Base44 app contains valuable screens, workflows, player records, statistics and business rules that must be assessed and safely exported. • The finished technology must be owned and controlled by BCA, without permanent dependence on Base44 or any individual developer. • Camera-based automatic scoring is a future project and is not included in this first stage. FIRST ENGAGEMENT Stage 1 – Paid discovery and migration audit • Review the existing Base44 application, entities, functions, integrations and available source code. • Identify all data, business rules and dependencies that must be preserved. • Produce a recommended architecture and migration plan. • Identify immediate risks involving data integrity, security, ownership and deployment. • Provide a realistic milestone estimate for the first scorer release. • Confirm what can be reused and what should be rebuilt. Stage 2 – First production scorer vertical slice The first working release should demonstrate one dependable end-to-end journey: • BCA-owned user authentication and player identity. • Create and join a two-player 501 darts match. • Correct throw order, double-out and bust rules. • Record each visit as an immutable scoring event. • Undo or correct an entry without deleting its audit history. • Live synchronisation for the opponent and spectators. • Protection against duplicate submissions and conflicting device updates. • Offline score queue with safe reconnection. • Completed match history saved against both players. • Accurate match average, First 9 average, checkout, legs and breaks-of-throw statistics. • Automated tests covering the core scoring rules. • Monitoring, backups and documented deployment. REQUIRED EXPERIENCE Applicants must personally demonstrate substantial experience with: • React and TypeScript. • Node.js backend development. • PostgreSQL or an equivalent relational database. • Real-time shared application state using WebSockets or a similar technology. • Authentication and role-based access. • Offline-capable web applications/PWAs. • Automated testing, deployment, monitoring and backups. • Database transactions, idempotency and protection against race conditions. Sports or darts experience would be helpful but is not mandatory. Strong engineering experience with live shared state and permanent transactional data is more important. A portfolio consisting only of standard websites, landing pages or WordPress projects will not be suitable. OWNERSHIP AND WORKING ARRANGEMENTS • All work must take place in repositories and service accounts owned by BCA. • BCA must own the source code, database, deployment environments and project documentation. • The agreement must assign all project-specific intellectual property to BCA. • Any open-source or third-party dependencies must be declared. • Unapproved subcontracting is not permitted. • Milestones will only be released after agreed acceptance tests pass. • The engagement must include documentation, handover and an agreed defect-remedy period. • No production player data should be copied into personal developer accounts or unmanaged environments. PROPOSAL REQUIREMENTS Please include: Two relevant examples of production systems you personally built involving real-time shared state, offline behaviour or transactional data. Your proposed approach to the paid discovery. How you would prevent duplicate score submissions and simultaneous device updates from corrupting a match. Your recommended technical architecture and why. Your estimated cost and timescale for discovery separately from the scorer build. Your availability and the name of the person who will perform the work. Two client references or relevant verified Upwork contracts. Any assumptions, exclusions and expected ongoing hosting costs. Please begin your proposal with the words “BCA SCORER” so we know you have read the complete brief. We value clear communication, honest technical advice and dependable delivery. If the first stage is successful, there is substantial potential follow-on work involving player profiles, rankings, online leagues, memberships, notifications, venue tools and further migration from the existing system.