Senior MERN Developer (React.js + Node.js)

Headquarters: Sweden
URL: http://career.proxify.io

The Role:

We are looking for a Senior MERN Stack Developer with heavy specialization in React.js and Node.js on behalf of one of our high-growth clients to architect, scale, and maintain high-throughput web applications. In this role, you will take operational ownership of both front-end user interfaces and back-end microservices, delivering seamless, secure, and responsive digital products. You will bridge user-facing features with complex database architectures and cloud infrastructure. You are a perfect candidate if you are growth-oriented, you love what you do, and you enjoy working on new ideas to develop exciting products

What we are looking for:

• 5+ years of professional software engineering experience designing, building, and deploying end-to-end applications using MongoDB, Express.js, React.js, and Node.js.
• Deep proficiency in modern JavaScript (ES6+), TypeScript, asynchronous programming, event loops, and memory management across client and server environments.
• Deep mastery of React internals, custom hooks, component design patterns, state management (Redux Toolkit, Zustand, or React Query), SSR/SSG frameworks (Next.js is a strong plus), and performance optimization (virtualization, code splitting, Web Vitals).
• Proven experience architecting scalable RESTful APIs, WebSockets, and/or GraphQL services. Proficiency with middleware design, authentication protocols (JWT, OAuth2, Passport.js), and event-driven architectures.
• Advanced knowledge of MongoDB schema design, aggregation pipelines, index strategy, performance tuning, and ORMs/ODMs like Mongoose or Prisma.
• Strong commitment to test-driven development using frameworks like Jest, React Testing Library, and Cypress, alongside hands-on experience with Docker, CI/CD pipelines (GitHub Actions), and AWS cloud services.
• Time zone: CET (+/- 3 hours). We are unable to consider applications from candidates in other time zones.

Nice-to-have:

• Experience with Next.js or Remix for production-grade full-stack React frameworks.
• Familiarity with relational databases (PostgreSQL, MySQL) alongside MongoDB.
• Experience with vector databases or AI model integration into Node.js backend services.
• Exposure to micro-frontends or monorepo setups (Turborepo, Nx).

Responsibilities:

• Design, develop, and deploy scalable full-stack features from initial database schema creation down to polished, pixel-perfect React interfaces.
• Build secure, high-concurrency microservices and web services, managing integrations with third-party APIs, webhooks, and real-time communication channels.
• Audit, profile, and optimize application throughput—reducing bundle sizes and rendering overhead on the front end while optimizing database queries and caching layers (Redis) on the back end.
• Lead architectural discussions, write modular and well-documented TypeScript code, enforce strict testing protocols, and conduct thorough peer code reviews.
• Collaborate with cloud and DevOps engineers to containerize applications, set up automated deployment pipelines, and maintain system monitoring tools.

What we offer:

To apply: https://weworkremotely.com/remote-jobs/proxify-ab-senior-mern-developer-react-js-node-js