Senior Product Engineer , Fullstack

This role is based out of our Amsterdam office 🇳🇱 or London office 🇬🇧 We are a hybrid company & believe great products are made when we are together. About Stacks Stacks is building an AI-native platform that reinvents how modern finance teams run the monthly close. The opportunity is massive: every growing company depends on accurate, timely financial data, yet most are still operating with tools and workflows built for a different era. In just two years, we’ve grown from a team of 2 to 30+ and are on a rapid trajectory towards $10m ARR. We’ve raised a $23m Series A led by Lightspeed Venture Partners , and we were recently recognised as one of Harmonic’s Hottest Startups of 2026 . We’re already trusted by leading European scale-ups including Pleo, Freetrade, and Motorway. Our team is a blend of finance, product, and technical experts from top-tier companies like Uber, Plaid, Miro, Mollie, and Bunq, united by the drive to create a game-changing solution. We’re a team that is deeply customer-obsessed, plays to win, and isn’t afraid to take big, bold bets. We move fast, hold a high bar, and are committed to growing together as we scale. 🔎 About the Role At Stacks, a Founding Product Engineer is a customer-obsessed, product-focused engineer who owns outcomes end to end, from customer conversation to production. You are driven by results, not tasks. You are passionate about solving real customer problems and constantly iterating to create elegant solutions. 🧱 What You'll Do Operate as a high-agency engineer who owns outcomes, not just implementation — driving features from idea to production, making thoughtful product tradeoffs with PMs, leading rollout and adoption, jumping on customer pain points early, and pushing for a seamless product experience. You will join customer calls alongside product, sit with finance leads, learn what is actually painful, and come back with a plan to fix it. The insights you gather directly shape what you build next. You will make architectural decisions that matter, define data models, design APIs, and set patterns the rest of the team builds on. When something breaks in production, you own it. As one of the earliest engineers on the team, you will also help set the bar. The way you write code, review others, and approach problems will define the culture of the team as it grows. Our product and technology are always evolving, so being a fast learner matters more than knowing our stack on day one. Here is what we are currently building with: Frontend: React, Next.js Backend: Node.js, Express, TypeScript, Python, Protobuf Data and Infrastructure: PostgreSQL, Redis, Google Cloud Platform, Terraform 🧩 What You Need Ownership and DRI mindset: You own problems end to end, create clarity when none exists, and take responsibility for outcomes without waiting to be told what to do next. Full stack depth with a backend focus: Strong TypeScript and Node.js fundamentals, comfortable across the stack, solid on API design, async processing, failure handling, and data modelling. Judgment under ambiguity: You make high-quality trade-offs between speed, correctness, and long-term system health. You choose simple and scalable where others over-engineer. Product and customer mindset: You think in customer problems, not tickets. You have talked to users and used what you learned to change what you built. Learning speed: You close gaps independently and with urgency. You do not need a long ramp-up or structure to orient yourself. Execution and reliability: You have shipped things that mattered and felt personally responsible when they did not work. You design for failure from the start. Influence and leverage: You make the engineers around you faster and better through how you write code, share context, and raise issues. 🚀 What’s in It for You Foundational role: Help shape a category-defining company from an early stage, working directly with founders and a small, high-agency team. Cutting-Edge Technology: Work at the forefront of the AI revolution in a product where AI is core, not bolted on Meaningful ownership: Competitive equity in a company scaling rapidly towards $10m ARR, where your impact will directly shape the outcome. Cutting-edge product and tech: Work at the intersection of AI and finance, building systems that fundamentally change how companies run their financial close. High-calibre team: Collaborate with people from companies like Uber, Plaid, Miro, and Mollie. Exceptional workspace: Our London HQ is based in Fora — a modern, design-led space in the heart of the city with access to a gym, classes, and an environment built for focused, in-person building Strong team culture: We run regular socials and off-sites that bring the team together properly, we recently have our 2-year anniversary party in Amsterdam, with board games, a tarot card reader and live music 🎶 🤝 The Hiring Process We move fast. Most candidates complete the full process within two weeks Step 1: 30 min intro chat with our TA team to learn more about Stacks and get genuinely excited about what we are building Step 2: 45 min product and tech chat to explore how engineering and product collaborate at Stacks and what ownership really looks like here Step 3: 60 min coding session, a focused moment for you to tackle a real engineering problem the way you would on the job Step 4: 60 min system design, your chance to show how you translate product requirements into technical architecture and make trade-offs that matter Step 5: 45 min onsite conversation with our Founder about Stacks culture, values, and the journey ahead Step 6: Offer. If we have gotten this far, we are excited about you and we will make that clear