Senior Full-Stack Developer (Node.js+React)

N-iX is looking for a Full-Stack Engineer (Node.js+React) for a London-based fintech startup building a digital marketplace for the secondary private credit market. The platform enables institutional investors to buy and sell credit positions, co-invest in large deals, access liquidity before loan maturity, and receive AI-generated deal tear sheets and fair asset valuations. You’ll join a three-person full-stack engineering team covering backend (distributed systems, multi-threading), frontend (UX/UI), and DevOps (AWS architecture, observability, CI/CD).

Requirements

• 5+ years of commercial experience as a Full-Stack Developer.

• Strong expertise in JavaScript/TypeScript with proven experience building web applications using React, Next.js, Styled Components.

• Solid backend experience with Node.js, databases (MariaDB/MySQL, DynamoDB, MSSQL, ElasticSearch), and GraphQL.

• Knowledge of AWS (Lambda) and microservices architecture.

• Hands-on involvement in CI/CD, QA, and testing activities.

• Upper-Intermediate+ English proficiency.

• Comfortable working independently and engaging directly with stakeholders to clarify requirements.

Nice-to-Have

• Experience in fintech or credit/loan-related platforms.

• Familiarity with observability tools (Datadog, Prometheus).

• Exposure to distributed systems and multi-threading.

• Strong understanding of performance and scalability challenges in financial systems.

Key Responsibilities

• Deliver high-quality features covering both functional and non-functional requirements (security, performance, scalability).

• Participate in technical discussions and own key technical decisions, ensuring alignment with best practices.

• Design and implement end-to-end features across frontend and backend in a fast-paced environment.

• Communicate effectively with both technical and non-technical stakeholders on a daily basis.

• Refine requirements, manage dependencies, and contribute to backlog prioritization and planning.

• Engage independently with stakeholders to translate business needs into working solutions.

• Contribute to platform improvements and technical strategy.

• Drive engineering quality by reviewing code, contributing to testing, CI/CD, and QA processes.