Staff Product Engineer in London

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, Meta, 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

Stacks is looking for a Staff Product Engineer to set the technical standard for how we build. This is not a management role. It is an individual contributor role with outsized influence, where your decisions shape architecture, unblock teams, and define what great looks like across the entire engineering organization. You will work at the intersection of complex technical problems and real customer outcomes. You will be the person others come to when the problem is hard, when the trade-off is unclear, or when the stakes are high. You will define the approach, not just execute it.

🧱 What You'll Do

• Own the most technically complex and highest-impact problems in the product, end to end, from architectural vision through to production reliability.
• Define technical direction across the engineering team: set patterns, establish standards, and make foundational decisions that others build on for years.
• Lead cross-functional technical discussions, partnering closely with product, design, and the founding team to translate ambiguous problems into elegant, scalable solutions.
• Join customer calls and engage directly with finance leads and CFOs. You will bring technical depth to commercial conversations and use what you learn to sharpen what we build.
• Identify and resolve systemic risks before they become production incidents. You design for failure, not around it.
• Raise the bar for the whole team: through code reviews, technical mentorship, and by modelling what rigorous, thoughtful engineering looks like in practice.
• Lead by example as an active contributor: not only setting technical direction, but consistently writing production code, raising the bar in code reviews, mentoring engineers, and evolving AI-native engineering workflows.

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.

🤝 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 system design, your chance to show how you translate product requirements into technical architecture and make trade-offs that matter.
• Step 4: 60 min coding session, a focused moment for you to tackle a real engineering problem the way you would on the job.
• 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.