Backend Architect & Lead Developer

Description: We're building Grit, a multi-tenant youth-sports team management platform (React Native mobile app + two web admin consoles) operated by a for-profit software company on behalf of many independent coaching teams. We have a complete, detailed technical specification already written — data model, API surface, permission rules, and a phased build order — along with working front-end prototypes for every screen. We need a senior backend developer to architect and build the real backend from this spec, starting with authentication, multi-tenant team/role management, and the permission-enforcement layer that everything else depends on. This is a lead role: you'll be the technical point of reference other freelancers on later postings build against, so strong system-design judgment matters as much as raw coding speed. Scope for this engagement: Auth (email/SMS/social), team creation, invitation flows, role assignment (Head Coach, Assistant Coach, Athlete, Parent, Non-Profit Admin, Platform Operator) Server-side permission guard middleware — role checks, suspension/freeze checks, and per-flag Assistant Coach permission checks, enforced centrally, not per-endpoint Append-only audit logging with database-level write protection Core data model implementation in PostgreSQL (or your recommended equivalent) matching the provided spec Required experience: 5+ years backend development, Node.js/TypeScript preferred (spec assumes NestJS but open to your recommendation if you can justify it) Real experience building multi-tenant SaaS systems — this isn't a single-org app, and tenant isolation has to be correct from day one Strong PostgreSQL/relational database design skills Comfortable reading and working from a detailed existing spec rather than defining requirements yourself Prior experience with role-based access control (RBAC) systems, ideally with per-feature permission granularity, not just fixed role tiers Deliverables: Deployed API (staging environment), API documentation, and a short technical handoff doc for the developers who'll build on top of your work in later phases.