Senior Product Engineer

WHY POLAR? It's never been easier to build, ship and scale software. But it's never been harder to monetize it. Modern startups look fundamentally different than prior generations: * Smaller teams * Exponential revenue growth relative to headcount * Higher variability in costs (LLMs) requiring more frequent pricing iterations * Laser focused on product development and distribution * Delegating and automating everything that is boilerplate – be it in their codebase or business operations. Exceptional billing primitives, APIs and SDKs are essential, but delightful integration is not enough. Startups need a billing platform designed for their speed of iteration. Combining billing and analytics in one platform to offer customer- and feature unit economics in real-time. Offering built-in pricing and cost insights, simulations and optimizations while simultaneously handling international compliance, tax management, fraud prevention and more. That's Polar. We're building the next standard for applied AI startups. Join our small, talented and engineering-led team across Europe as we build the infrastructure powering the next generation of software companies. We focus on shipping at high velocity to serve startup founders scale their businesses. Everything else is secondary. ROLE & RESPONSIBILITIES: WHAT YOU WILL DO We’re hiring a Senior Platform Engineer to architect and evolve the Polar platform - ensuring the system remains fast, resilient and operationally sound as we scale. Polar operates as a merchant of record, meaning our platform sits directly in the critical path of global payments, billing infrastructure and financial workflows. Reliability, uptime and correctness are essential - while still maintaining the ability to move quickly and ship product improvements. You’ll work across the platform and infrastructure layers that power Polar - from core infrastructure and observability to deployment safety, internal tooling and reliability engineering. In close partnership with the team, you’ll ensure the system scales to handle increasing traffic, architectural complexity and regulatory demands without compromising stability, performance or developer velocity. This role is ideal for someone who treats reliability as a product requirement and scalability as an architectural discipline, combining deep systems engineering experience with a passion for building reliable, scalable platforms and empowering engineering teams through strong abstractions and automation. While this role focuses primarily on the foundational layers of our platform, we value engineers who are comfortable moving across the stack when needed to ship quickly and maintain momentum. You’ll work with the team to: * Ensure Platform Reliability & Uptime: Design and evolve systems that maintain high availability, predictable performance and operational stability. Drive improvements in uptime, resilience and operational discipline as the system scales. * Engineer for Scale & Performance: Strengthen how our distributed services behave under load. Identify bottlenecks, optimize critical paths and design systems that scale with growing traffic and complexity. * Advance SRE & DevOps Practices: Embed reliability engineering practices across the platform - defining SLOs and SLIs, improving incident response, reducing operational toil and making production behavior measurable and actionable. * Evolve Cloud & Infrastructure Systems: Continuously evolve Polar’s infrastructure baseline and determine when the current stack needs to evolve. Improve infrastructure-as-code, environment management and operational safety mechanisms. * Strengthen Deployment & Operational Safety: Refine CI/CD systems, rollout strategies and rollback mechanisms to ensure changes are safe, observable, reversible and fast to deploy. * Improve Observability & Debuggability: Advance logging, metrics and tracing standards so engineers can quickly understand, debug and resolve issues in production. * Collaborate across Engineering, Risk & Legal: Work closely with product and infrastructure engineers, as well as risk and legal stakeholders, to translate evolving regulatory requirements into clear technical abstractions while maintaining long-term platform reliability and health. WHAT WE’RE LOOKING FOR Systems Thinking & Operating Mindset * Deep systems thinking: You anticipate failure modes, design for idempotency and consistency, and think carefully about how distributed systems behave in production. * Security- and compliance-aware engineering mindset: You build with auditability, principled access control and regulatory constraints as first-order design considerations. * End-to-end ownership: You are comfortable owning features from infrastructure and backend systems all the way to shipping functionality that powers the product. While this role focuses on platform layers, we value engineers willing to work across the stack when needed. * Strong product judgement: You know when to move fast while ensuring that correctness, auditability and long-term system integrity take precedence. * High-ownership collaboration: You thrive in small teams, collaborating closely across engineering to evolve the platform architecture and take shared responsibility for the long-term health of the system. Technical Skills * Strong backend expertise - you design clear, durable APIs and build systems that are resilient under real-world load and edge cases. * Highly proficient in SQL and data modeling - you reason rigorously about long-term data correctness, performance and reliability across large datasets. * Strong production debugging and observability instincts with an ability to trace complex issues across services and understand how to prevent them in the future. * Experience building or operating distributed systems with strong reliability and operational requirements. Experience * 5-8+ years of engineering experience, building and scaling customer-facing SaaS or fintech products in a high-growth environment. * Experience in payments and billing infrastructure - subscription lifecycles, transaction orchestration, refunds/disputes, payouts and financial state management. Nice-to-have: Open source contributions or side projects/apps to showcase. WHAT WE OFFER * Meaningful ownership: Small team & large surface area. You’ll directly influence how the company and platform scale. * Product-driven culture: We build to empower the next generation of software companies - and operate with the same builder mindset internally. * Competitive compensation: Salary and equity aligned with the impact of the role. * Exceptional team: Work with highly talented team members distributed across Europe. * Remote-first environment: Work from anywhere in Europe, with a home office setup budget available. * Annual team offsites: As the team is spread across Europe, we gather in person at least once a year to collaborate, plan, and spend time. * Health Benefits: Comprehensive health coverage to support you and your family. * Parental leave: Paid parental leave aligned with the standards and regulations of your local jurisdiction. HOW WE HIRE Polar is a remote-first company, with team members across Europe, and our hiring process is fully remote via video calls and email. HIRING PROCESS 1. Application Review: We review your application and previous work. 2. Intro call: A short conversation with Birk (Founder and CEO) to learn more about you and give you a chance to learn more about Polar. 3. Take-home Assignment: A practical exercise designed to reflect the kind of problems you would work on in the role. 4. Assignment Review: We review your assignment and feedback together 5. Team Conversations: 2-3 video calls where you get the chance to meet future team members. 6. Offer 🎉 7. Reference Calls

**This is a remote position open to candidates in Europe. For those based in the Czech Republic, a hybrid work model is also available. ABOUT US We are a leading product development partner specializing in custom web and mobile application development. With Silicon Valley founders and top-tier European tech talent, we operate from Prague and have successfully delivered over 65 software products for early-stage startups, scaleups, and global enterprises. * Founded in 2016 * Headquartered in Prague * Built and launched 65+ products * 90+ team members * Driving product innovation for leading US companies At OAK’S LAB, we take an AI-first approach, utilizing AI on almost every project. From streamlining design and testing workflows to enhancing developer productivity, our teams leverage tools such as Figma MCP Server, Playwright MCP Server, and Cursor, and we’re actively experimenting with remote AI agents to push the boundaries of what’s possible in product development. OUR PROJECTS Here are a few from our portfolio: * Nasdaq Private Market (Series C, Finance)- nasdaqprivatemarket.com * Blackpoint Cyber (Series B, Cybersecurity) - blackpointcyber.com * OpenLoop (Series A, Healthcare) - openloophealth.com THE ROLE Our product development team is looking for a Senior Fullstack Engineer who combines creative thinking, exceptional problem-solving skills, and technical expertise to build outstanding web and mobile applications for our clients. You’ll play a key part in building and scaling impactful digital products from the ground up. You’ll work as part of a dedicated product team alongside a Tech Lead, Product Manager, Designer, and a talented group of engineers, driving the success of innovative companies. Your role will involve everything from participating in high-level technical discussions to engineering and deploying complex features, giving you full ownership across the entire product development lifecycle. For ambitious engineers, we’ll provide the time, mentorship, and opportunities to step into a leadership role, where you can guide and mentor your own team over the longer term. You’ll also have the opportunity to join our internal AI Guild, a community where engineers share insights, experiment with cutting-edge AI tools, and learn from one another. RESPONSIBILITIES * Design, develop, and version high-quality web and mobile applications * Collaborate with product teams to understand feature requirements and translate them into technical solutions * Be accountable for an area of the application, its delivery, production-level quality, and its effective presentation to stakeholders * Understand the product and user needs to prioritize business value and functionality * Ensure the application meets all requirements of security and scalability * Write clean and scalable code * Engage in code reviews, provide constructive feedback, mentoring less senior engineers SKILLS & REQUIREMENTS * 5+ years of experience in building web solutions using Node and React * Experienced with Javascript/Typescript * Focus on code quality * Desire to learn new technologies and apply AI in your workflow * Strong analytical and problem-solving skills * Proactiveness and the capability to make a difference * Driven, hard work ethic, showing commitment * Ability to work effectively in a team environment, following Agile methodologies * Proficient in English * Experience with Python is beneficial but not essential OUR TECH STACK * Typescript * Node.js * React + Next.js * React Native * GraphQL, tRPC * Material UI * Playwright * PostgreSQL * Google Cloud Platform * Python * HuggingFace API, LLM APIs (eg OpenAI API), Langchain, Vector Databases for RAG Important Notice: OAK'S LAB communication, including interview requests and job offers, are only sent from an "@oakslab.com" or "@oaks-lab.com" email addresses (e.g., john@oakslab.com or john@oaks-lab.com). Any message from a different email domain is not associated with OAK'S LAB. We will never ask for payment information or banking details via email, phone, or any other communication channel during the interview process. If you receive messages using our name, domain, or brand assets in an attempt to impersonate us or act on our behalf, do not engage. Instead, report it to Econsumer.gov at Government Shutdown Notice / Aviso de cierre del gobierno (if you are in the EU), Federal Trade Commission (FTC) at Government Shutdown Notice / Aviso de cierre del gobierno , or the Securities and Exchange Commission (SEC) in case of investment fraud at SEC.gov | Report Suspected Securities Fraud or Wrongdoing (if you are in the US).