Senior Backend Engineer (Node.js)

Scrambly; Denmark; On-site; DKK 800,000 - 1,200,000; Full time

Job summary

Scrambly is seeking a Senior Backend Engineer to build core systems powering a high-growth adtech platform serving millions of users globally. You will work across user-facing product systems and internal tooling, focusing on robust, high-performance code and scalable architectures.

You should excel in Node.js and NestJS, design RESTful APIs, and collaborate with Product, Design, and QA to translate requirements into reliable technical solutions.

Qualifications

• 5+ years of software engineering experience with a backend focus.
• Strong proficiency in Node.js and NestJS.
• Excellent system design skills and backend architecture knowledge.
• Cloud experience with GCP preferred; AWS or Azure acceptable.
• Containerization and orchestration: Docker, Kubernetes, Terraform, Helm.
• Databases: PostgreSQL and Redis; messaging with RabbitMQ or Pub/Sub.
• Frontend autonomy with React for internal tools.
• Strong communication and collaboration in fast-paced teams.
• English: Upper-Intermediate or higher (B2+).

Responsibilities

• Architecture & Development: design, build, and maintain highly scalable Node.js (NestJS) RESTful APIs and distributed systems.
• Quality & Mentorship: code reviews and pair programming.
• Infrastructure & Performance: monitor reliability, optimize CI/CD pipelines.
• Cross-Functional Collaboration: translate requirements with Product, Design, and QA, and communicate constraints clearly.

Skills

Node.js

NestJS

RESTful APIs

Distributed systems

React

English communication

Tools

Docker

Kubernetes

Terraform

Go basics

Job description

About The Company

Scrambly is one of the fastest-growing adtech startups in the world, featured in the AppsFlyer Performance Index and Singular ROI Index in just 3.5 years. We’re growing 250%+ YoY across revenue, team, product, and technology — fully bootstrapped and profitable. We’re building the future of app discovery: a reward-powered alternative to the App Store and Google Play. Our loyalty-driven ecosystem connects millions of users with the world’s top apps and delivers unmatched, ROI-focused growth for mobile advertisers. Our mission is to build a true alternative to traditional app stores — fueled by rewards and data — and create a new, performance-first growth engine for mobile app advertisers.

About The Role

We are looking for a Senior Backend Engineer to join the team building the core systems behind Scrambly. In this role, you will work across two key areas: user-facing product systems, solving complex scalability challenges for a platform serving millions of users globally, and the internal platform, covering admin systems, tooling, and back-office automation that power our operations team. Your focus will be on writing robust, high-performance code and bridging the gap between product requirements and technical reality. You will work within a modern tech stack to ensure our systems remain fast, reliable, and easy to maintain as we grow.

Key Responsibilities

• Architecture & Development: Design, build, and maintain highly scalable Node.js (NestJS) RESTful APIs and distributed systems. Ensure seamless frontend integration and drive long-term architectural improvements.
• Quality & Mentorship: Champion clean, testable code standards and foster a culture of technical curiosity by mentoring engineers through code reviews and pair programming.
• Infrastructure & Performance: Monitor system reliability, resolve bottlenecks, manage containerized application lifecycles, and partner with DevOps to optimize CI/CD pipelines.
• Cross-Functional Collaboration: Partner with Product, Design, and QA to translate requirements into robust technical specs, while clearly communicating technical constraints to non-technical stakeholders.

Requirements

• Experience: 5+ years of software engineering experience, with a strong focus on backend development.
• Tech Stack: Strong proficiency in Node.js and modern frameworks like NestJS.
• System Design: Excellent system design skills and a solid understanding of backend architecture, RESTful APIs, and distributed systems.
• Infrastructure: Experience with cloud platforms (GCP preferred; AWS or Azure acceptable), containerization (Docker), and orchestration/IaC (Kubernetes, Terraform, Helm).
• Databases & Messaging: Proficiency with relational (e.g., PostgreSQL), NoSQL (e.g., Redis) databases, and message queues (e.g., RabbitMQ, GCP Pub/Sub, Redis Pub/Sub).
• Frontend Autonomy: Hands-on experience with React, capable of implementing basic UI features for internal tools independently.
• Collaboration: Strong communication and collaboration skills, comfortable working in a fast-paced team environment.
• English: Upper-Intermediate or higher (B2/B2+, written and spoken). You need to be able to communicate clearly in English to work effectively in an international team and participate in architectural discussions

Nice to Have

• Scale: Experience in a B2C startup that has scaled to millions of users.
• Additional Stack: Basic proficiency in Go; able to read, write, and maintain basic Go services without starting to learn from scratch.

What We Offer

• Work on systems where performance optimizations translate to immediate user impact for millions of users.
• A culture of code reviews, knowledge sharing, and mentorship where the best idea wins.
• A fast-paced environment where your code quickly translates into real user value.
• We value the stability and value of what you ship, not just the number of lines of code.