Full Stack Developer
4 days ago
Upminster
\n 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. \n 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. \n 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. \n 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. \n What you'll do \n\n • Build 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.\n, • Develop Back End features in Node.js, including a Fastify API, an Express Back End-for-Front End and durable background jobs processed through a SQL-backed outbox queue.\n, • Design and evolve the SQL Server schema through forward-only migrations, using parameterised queries and transactional business logic.\n, • Integrate and mock third-party services, including identity-verification and lead-management providers, while keeping transport details behind well-defined interfaces.\n, • 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.\n, • 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.\n, • Work collaboratively to document technical decisions, follow established conventions and improve the platform as it grows.\n\n What you'll bring \n\n • At least three years of professional JavaScript development experience, with meaningful hands-on work across both Front End and Back End development.\n, • Strong React fundamentals, including hooks, controlled forms, routing and state management, together with confidence using modern ESM tooling.\n, • Experience building and consuming REST APIs in Node.js using Fastify, Express or a comparable framework.\n, • Practical SQL knowledge covering schema design, joins, transactions and indexes. SQL Server experience is helpful but not essential.\n, • A genuine testing habit: you write useful tests because they prevent defects and support confident delivery, not simply because the CI pipeline requires them.\n, • Clear written communication and the ability to document decisions, explain trade-offs and work within established conventions.\n\n Nice to have \n\n • Experience working on multi-tenant or multi-brand products.\n, • Familiarity with queue or outbox patterns, Redis, PM2, nginx or Cloudflare.\n, • Exposure to regulated industries such as financial services or insurance, or experience with KYC and identity-verification journeys.\n