Senior Backend & Data Systems Engineer | Node.js, TypeScript, PostGIS

We're looking for a senior backend and data systems engineer to own a substantial part of a production data platform. You will work directly with the founders in a small engineering team, make architecture decisions, deploy your own work and take responsibility for how it runs. The work involves large-scale ingestion of changing public records, resolving incomplete or conflicting records to the right address, site or property, and turning geospatial source data into reliable, versioned datasets. This is an ongoing engineering role, not a one-off scraping task. WHAT YOU WILL OWN - Ingestion pipelines: throughput, reliability, recovery, change detection and the tooling needed to keep sources current. - Entity resolution: matching incoming records to the correct entities, improving coverage and measuring the quality of those matches. - Geospatial data products: source acquisition, processing, validation, versioning and delivery using PostGIS and supporting pipelines. - Architecture and production delivery in your domain, including testing, monitoring and incident diagnosis. - Clear documentation of decisions, trade-offs, operating procedures and failures. WHAT YOU NEED - Strong production experience with Node.js and TypeScript, backed by systems you have built and operated. - SQL beyond an ORM: query plans, indexing, performance and the cost of writes at scale. - Experience with retries, idempotency, deduplication, backfills and changing source data. - Practical PostGIS or comparable geospatial experience: spatial queries, coordinate systems and geometry validation. - The ability to investigate production problems independently and fix the underlying cause. - Clear written English, especially when explaining uncertainty, failures and technical decisions. - Fluency with current AI development tools and the judgement to verify their output. Python is useful, but not essential. We can teach the rest of our stack. HOW WE WORK Remote, with flexible hours and an agreed overlap with the UK team. Decisions and post-mortems are written down, and changes are measured before they ship. You will have direct access to decision-makers, current frontier models, inference infrastructure and the tools the work needs. ENGAGEMENT An initial contract with a review at an agreed point, with the intention of a long-term relationship if it works for both sides. The rate is negotiated individually at senior-market level. Any completion payment for accepted delivery and handover will be agreed upfront and paid through Upwork. There is room to grow into end-to-end technical ownership, contribute to hiring and progress along either a senior technical or leadership path. Any future employment arrangement would be subject to mutual agreement and Upwork's contract-to-hire requirements; employment benefits and equity would be separate from the initial freelance contract. HIRING PROCESS We aim to complete four stages within two weeks and decide within 48 hours of the final stage: 1. A short written exchange through Upwork about three relevant engineering problems. 2. A 45-minute introductory conversation using Upwork's communication tools. 3. A paid working session on sanitised data, using your normal tools and completed in your own time. We will agree the day rate and put an Upwork contract in place before any assessment work starts. 4. A 45-minute walkthrough where we discuss your solution and work through a changed requirement together. No unpaid assessment work. Applications, communication, contracting and payments will be handled through Upwork. TO APPLY Send a short introduction, relevant examples from your track record, your proposed rate, availability and the UK-hours overlap you can offer. Please explain what you personally owned and the scale and outcome of the systems involved.