At Similarweb, we are revolutionizing the way businesses interact with the digital world by revealing to them everything that happens online.

Our unique data and solutions empower over 4,300 customers globally, including industry giants like Google, eBay, and Adidas, to make game-changing decisions that drive their digital strategies.

In 2021, we went public on the New York Stock Exchange, and we continue to reach new heights! Come work alongside Similarwebbers across the globe who are bright, curious, practical and good people.

We are looking for a Senior Fullstack Engineer with a strong backend orientation to join the development of our scalable, AI-powered product systems.

What You'll Do:

Join a role that combines deep backend expertise with solid frontend fluency and product thinking, along with the ability to leverage AI tools effectively across the development lifecycle. You will work closely with product, design, frontend, and data/AI teams to build reliable, performant systems and intuitive user experiences, while driving engineering excellence and modern development practices. Your contributions will shape the technical foundation of an AI-first product and directly influence the experience of end users.

What does the day to day of a Senior Fullstack Engineer at Similarweb look like:

Your daily work will span backend architecture, frontend collaboration, and AI-augmented development, engaging directly with the systems that power our product.

Your role will include:

• Design and build scalable, maintainable backend services using NestJS (Node.js/TypeScript) and/or Python
• Own API design, contracts, and versioning across services
• Design and optimize data models, database schemas, and query performance
• Implement authentication, authorization, and secure API integration patterns
• Build reliable data-fetching layers, caching strategies, and async processing (queues, jobs, events)
• Lead backend technical decisions, code quality standards, and system architecture
• Ensure system scalability, fault tolerance, and observability (logging, monitoring, alerting)
• Contribute to CI/CD pipelines and deployment practices for backend services
• Collaborate on frontend applications built with React, TypeScript, and Vite, and contribute to API contracts from the consumer's perspective
• Partner with frontend engineers to align on data shapes, performance, and UX constraints
• Translate product requirements into robust, scalable technical solutions, working closely with product and design
• Conduct high-quality code reviews and drive architectural discussions and best practices
• Improve testing, observability, CI/CD, and system reliability across the team
• Use AI coding tools effectively in daily development work (Cursor, Copilot, Claude, ChatGPT, etc.), critically evaluating and refining AI-generated code, especially for backend logic and data integrity
• Design efficient personal/team workflows for AI-assisted development and contribute to engineering productivity through AI tooling and automation

What does the ideal candidate look like:

• 5+ years of fullstack engineering experience, with a strong backend focus
• Strong proficiency in Node.js, TypeScript, and NestJS; Python proficiency also welcome (or equivalent backend framework)
• Solid working proficiency in React and modern frontend fundamentals (HTML, CSS)
• Experience designing scalable backend architectures and data models
• Deep understanding of API design, authentication flows, and distributed system tradeoffs
• Experience with relational and/or NoSQL databases, including query optimization
• Strong understanding of system performance, reliability, and security best practices
• Experience with testing methodologies (unit, integration, E2E) and observability tooling
• Hands-on experience using AI development tools in daily workflows, with the ability to validate, debug, and improve AI-generated code
• Understanding of prompt engineering for engineering workflows and the ability to work effectively in fast iteration environments
• Strong product and technical intuition, with excellent communication and collaboration skills
• Nice to have: experience with data platforms, analytics products, or BI tools; large-scale data processing or query optimization; streaming/real-time data patterns; or integrating with LLM APIs

Why you'll love being a Similarwebber:

You'll actually love the product you work with: Our customers aren't our only raving fans. When we asked our employees why they chose to come work at Similarweb, 99% of them said "the product." Imagine how exciting your job is when you get to work with the most powerful digital intelligence platform in the world.

You'll find a home for your big ideas: We encourage an open dialogue and empower employees to bring their ideas to the table. You'll find the resources you need to take initiative and create meaningful change within the organization.

We offer competitive perks & benefits: We take your well-being seriously, and offer competitive compensation packages to all employees. We also put a strong emphasis on community, with regular team outings and happy hours.

You can grow your career in any direction you choose: Interested in becoming a VP or want to transition into a different department? Whether it's Career Week, personalized coaching, or our ongoing learning solutions, you'll find all the tools and opportunities you need to develop your career right here.

Diversity isn't just a buzzword: People want to work in a place where they can be themselves. We strive to create a workplace that is reflective of the communities we serve, where everyone is empowered to bring their full, authentic selves to work. We are committed to inclusivity across race, gender, ethnicity, culture, sexual orientation, age, religion, spirituality, identity and experience.