Senior Full-Stack Engineer to Take Over Production SaaS (NestJS / React)

## About the role We are a B2B SaaS startup building a data-centric enterprise platform for corporate treasury and investor relations teams. Our MVP has been completed by an external development agency. We are now planning a structured transition to a senior, hands-on full-stack engineer who will take over post-MVP, ensure continuity, improve quality, and help shape the product's next phase. This is not a greenfield build and not a "move fast and break things" role. The focus is quality, security, maintainability, and thoughtful iteration. We are looking for a long-term partner (initially contract, with potential to extend significantly). ## Responsibilities - Take over day-to-day ownership of an existing production SaaS codebase - Work with the founder and fractional technical architect to: - review architecture decisions - stabilise and harden the platform - gradually improve code quality and test coverage - Deliver incremental product features and UX improvements - Ensure strong standards around: - security - access control - data integrity - auditability - Support early enterprise pilots and feedback-driven iteration - Collaborate with external vendors where needed (design, infra, audits) ## Current Tech Stack ### Backend - Node.js / TypeScript - NestJS (modular, service-oriented architecture) - PostgreSQL - REST APIs - Role-based access control (RBAC) ### Frontend - React - TypeScript ### Modern component-based UI (design system already defined) ### Infrastructure / DevOps - Cloud-hosted (GCP) - Docker - CI/CD pipelines - Environment separation (dev / staging / prod) ### Other - Multi-tenant SaaS architecture - Enterprise security mindset (GDPR, data isolation, logging) - No heavy AI/ML today (future roadmap item) ## Ideal Profile You are someone who: - Has 5–10+ years of professional experience - Has taken at least one SaaS product from MVP → production → real users - Is comfortable inheriting and improving an existing codebase - Thinks in terms of systems, not just features - Communicates clearly with non-technical founders - Is pragmatic, structured, and calm under ambiguity This role is not suitable if you: - Prefer greenfield projects only - Dislike working with existing architectural constraints - Want a purely short-term gig ## Engagement Details - Contract via Upwork - Initial scope: 6+ months - Expected workload: 15–30 hours/week - Strong likelihood of extension - Competitive hourly rate for senior talent ## Application Instructions (Important) Please include: - A short summary of similar SaaS products you've worked on - An example where you took over an existing codebase - Your experience with NestJS + React - Your preferred hourly rate and weekly availability