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:

Get paid, not played

No more unreliable clients. Enjoy on-time monthly payments with flexible withdrawal options.

Predictable project hours

Enjoy a harmonious work-life balance with consistent 8-hour working days with clients.

Flex days, so you can recharge

Enjoy up to 24 flex days off per year without losing pay, for full-time positions found through Proxify.

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One seamless process, multiple opportunities

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Compensation

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Senior MERN Developer (React.js + Node.js) at Proxify AB