Senior Backend Engineer (Python/FastAPI) — B2B Marketplace/SaaS Pre-Launch Platform Restructure

Summary We're a B2B PropTech marketplace connecting property managers and estate agents with verified service providers across the UK. The platform is built but not yet in production, and the backend is currently disorganised — inconsistent structure, technical debt, and integration work that needs to be reviewed, cleaned up, and made production-ready. We need a Senior Backend Engineer who can take a messy, partially built system and turn it into something scalable, secure, and reliable. This is a high-impact, fast-paced 2-month engagement. You'll be inheriting an existing, unorganised codebase — not a clean, well-structured platform in need of polish. Expect to spend real time understanding what's there, deciding what to keep, restructuring what's salvageable, and rebuilding what isn't, all under time pressure ahead of launch. Tech Stack • Backend: Python, FastAPI • Database: PostgreSQL • Infrastructure: AWS, Docker, Linux, Git, CI/CD • Integrations: Stripe Connect, REST APIs, CRM/PMS platforms, authentication services What You'll Be Doing • Taking ownership of a disorganised backend platform and restructuring it toward production readiness • Investigating and resolving complex backend, database, infrastructure, and integration issues • Building, improving, and maintaining integrations with Stripe Connect, CRM/PMS platforms, authentication providers, and other third-party services • Reviewing existing architecture, identifying what needs to be rebuilt vs. restructured, and executing on it • Managing AWS infrastructure, deployments, Docker environments, and CI/CD pipelines • Optimising PostgreSQL for performance, scalability, and data integrity • Writing clean, maintainable, well-tested code while untangling an inherited system under time pressure Who We're Looking For • Engineers with real experience owning production backend systems, not just contributing to them • People who've taken over a messy or unfamiliar codebase before and brought order to it, not just built greenfield systems • Strong analytical thinkers who can read a disorganised system quickly and make sound architectural calls without much guidance Requirements • 5+ years professional experience with Python and FastAPI • Strong knowledge of PostgreSQL, database design, and performance optimisation • Experience integrating third-party services (payment platforms, CRM/PMS, or similar APIs) • Hands-on experience with AWS, Docker, Linux, Git, and CI/CD pipelines • Strong understanding of REST APIs, authentication (JWT/OAuth), and backend architecture • Proven experience restructuring or stabilising an existing system, not only building new features • Ability to work independently, troubleshoot complex issues, and make decisions with limited direction • Available for a high-intensity, near full-time engagement for 2 months • Some overlap with UK working hours (BST) preferred Nice to Have • Stripe Connect experience specifically • SaaS or marketplace platform experience • Experience taking a pre-launch product from a rough or unorganised state to production Selection Process • Technical assessment focused on backend architecture and debugging • Final technical interview with the founding team