Full Stack Developer

If you are a Full Stack JavaScript Developer with a proven track record of developing single-page applications, we have a new role we would like to discuss with you. Please note this role requires onsite attendance four days a week in Upminster, Essex.The client is building a platform that guides consumers through the complete online customer journey, from their first visit through identity verification, e-signature and submission.As a Mid-Level Full-Stack JavaScript Developer, you'll work across the platform: a React single-page application on the front end, Node.js APIs and background workers on the back end, and Microsoft SQL Server as the system of record.This is a hands-on product engineering role where you'll ship customer-facing journey steps, build and consume REST APIs, write database migrations and integrate third-party services behind clean, maintainable interfaces.What you'll doBuild and maintain customer-journey screens and shared components in React 19, using React Router 7, Vite and Sass/SCSS across multiple branded sites from a single codebase.Develop back-end features in Node.js, including a Fastify API, an Express backend-for-frontend and durable background jobs processed through a SQL-backed outbox queue.Design and evolve the SQL Server schema through forward-only migrations, using parameterised queries and transactional business logic.Integrate and mock third-party services, including identity-verification and lead-management providers, while keeping transport details behind well-defined interfaces.Write meaningful tests at every layer: Vitest unit and route tests, Testing Library component tests, and Playwright end-to-end journeys against a real database running in Docker.Build with the needs of a regulated consumer product in mind, including robust input validation, careful PII handling, audit trails, idempotent retries and graceful degradation.Work collaboratively to document technical decisions, follow established conventions and improve the platform as it grows.What you'll bringAt least three years of professional JavaScript development experience, with meaningful hands-on work across both front-end and back-end development.Strong React fundamentals, including hooks, controlled forms, routing and state management, together with confidence using modern ESM tooling.Experience building and consuming REST APIs in Node.js using Fastify, Express or a comparable framework.Practical SQL knowledge covering schema design, joins, transactions and indexes. SQL Server experience is helpful but not essential.A genuine testing habit: you write useful tests because they prevent defects and support confident delivery, not simply because the CI pipeline requires them.Clear written communication and the ability to document decisions, explain trade-offs and work within established conventions.Nice to haveExperience working on multi-tenant or multi-brand products.Familiarity with queue or outbox patterns, Redis, PM2, nginx or Cloudflare.Exposure to regulated industries such as financial services or insurance, or experience with KYC and identity-verification journeys.