Lead Full Stack Engineer in London

We are on a mission to make it simple and affordable for every home in the UK to be heated and powered by clean, green electricity. Our customers are the installers who are at the forefront of this transition, but who have historically been overlooked and left struggling with outdated, ineffectual software. Since getting started at the beginning of 2024, we have grown exponentially, raised several rounds of funding from top-tier VCs, and now support over 500 heat-pump installation businesses across the UK. We are looking for an exceptional Lead Engineer to help us move faster and go further as we start to expand outside heat pumps.

Quick background on Spruce: We have started with the most challenging but ultimately most important part of the home energy transition: replacing boilers with heat pumps. Nearly 20% of the UK’s carbon emissions come from heating homes. There is no credible path to net-zero without replacing gas and oil boilers — and today, heat pumps are the only scalable alternative with their almost-magical ability to convert 1 kW of electricity into 4 kW of heat. The problem? The installation process is slow, fragmented, and painfully manual. This increases costs for homeowners, limits how fast installation businesses can grow, and makes it almost impossible to offer a heat pump when someone's boiler breaks down. We are fixing this. We have built an end-to-end operating system for heat-pump installers — from initial enquiry through design and installation to compliance and paperwork.

Relative to the best alternatives, Spruce now:

• Halves the time installers spend per job;
• Doubles sales conversion rates;
• Improves quality, margins, and customer experience;

And we are only just getting started. With fresh investment and growing demand, we are now expanding into the rest of the home renewables supply chain — supporting manufacturers and merchants as well as installers, and enabling solar & battery installations alongside heat pumps.

The Role: As a Lead Full-Stack Engineer, you will sit at the intersection of hands-on technical work, team leadership, and product strategy. You will still write a bunch of code — especially the hard, high-leverage parts — but your impact will increasingly come from setting direction, unblocking others, and raising the bar across the team. You will work closely with engineers, designers, and product leadership to ensure we are building the right things, in the right way, at the right time.

What You’ll Do:

• Own architecture and technical strategy for a core domain or set of systems;
• Design, guide, and build complex, cross-cutting solutions that span multiple parts of the product;
• Write high-leverage code: reference implementations, critical paths, foundational frameworks;
• Lead technical discussions, make trade-offs explicit, and help teams align;
• Mentor senior engineers and develop others into technical leaders;
• Coach engineers in how to make decisions, rather than making every decision yourself;
• Proactively identify scaling risks, bottlenecks, and areas of technical debt — and drive solutions.

Depending on your background, you may:

• Be stepping into your first formal lead role from a senior IC position, or
• Have already led teams successfully and want to stay close to the technical work.

The problem space: This is not CRUD-only work. You will be working meaningful production problems from day one that blends physical reality, real-world constraints, and serious impact:

• Heat loss modelling and hydronic system design;
• 2D and 3D floor-plan tooling using LiDAR and computer vision;
• Large-scale data ingestion and geospatial analysis;
• Offline-first, collaborative PWAs;
• Hardware integrations (Bluetooth measurement tools, sensors, monitoring systems).

Tech Stack: Our tech stack strives for simplicity, symmetry and efficiency. Our hard problems come from the real world instead of self-made architectural problems. You don’t need to know all of the below but you do need an appetite for full-stack mastery and owning the problem end to end:

• Docker, Docker Compose;
• PostgreSQL, PostGIS, Atlas migrations;
• Node, Prisma;
• React, TypeScript, Konva, Tailwind.

Requirements: We care less about titles and more about impact, judgment, and intent. You will likely have experience with:

• Modern JavaScript / TypeScript and frontend frameworks;
• Backend development and API design;
• Relational databases and data modelling;
• Solving ambiguous, real-world problems end-to-end;
• Mentoring and/or building healthy, high-trust teams.

But more importantly, you are:

• Product-mindful — you want to understand real users and real problems, not just tickets;
• Impact-driven — you balance technical quality with momentum and know when 'good enough' is exactly right;
• Comfortable with ownership — you take responsibility for outcomes, not just code;
• Candid and collaborative — you challenge ideas openly, receive feedback well, and optimise for the team over ego.

Benefits:

• Salary (£85-120k depending on experience, impact, and location);
• Meaningful slice of equity (options) in the company;
• 33 days holiday and opportunity to work from abroad for another 30 days each year;
• Hybrid working: Minimum 2 days in-person a week (London or Bristol);
• Workplace Nursery Benefit scheme (YellowNest);
• Cycle to Work scheme;
• Full-team meetups every fortnight with paid travel, accommodation and dinner;
• Brilliant team to learn from and massive opportunity to grow.

Working at Spruce: We are currently a close-knit team of 20, split evenly between London and Bristol. You will spend 2-3 days each week working together in-person in your nearest office, and we get everyone altogether every fortnight; You will have genuine influence from day one. The best idea wins regardless of seniority. We expect you to challenge everything, ask 'why?' multiple levels deep, and push back when something doesn’t make sense; We want everyone to spend time with installers on-site, feel their pain points, then be able to rapidly suggest and implement solutions based on real feedback rather than assumptions; We move fast and ship imperfect things, learning from users rather than trying to perfect in isolation. When things break, we focus on how we fix it, what can we learn and never blame. You will own your outcomes whilst knowing the team has your back; Feedback is constant, direct, and kind — we will tell you when something isn’t working and expect the same honesty (and empathy) back.

Application process: Initial video interview digging into your experience and your interest in this space; Take-home technical test; Technical interview; Final in-person team interview.

Seniority level: Mid-Senior level. Employment type: Full-time. Job function: Other. Industries: IT Services and IT Consulting.