Senior Backend Engineer in London

This role is based in London office, 5 days per week, no visa support is available. We're looking for a Backend Engineer to join an early-stage, revenue-generating AI-driven SaaS platform. You'll report directly to the Head of Engineering and own systems end-to-end. This is the sweet spot: early enough to design foundational systems, but with real customers, revenue from day one, and meaningful equity. You'll work in a small senior team where your code directly impacts business results.

Perfect for: Backend engineers who love owning systems end-to-end, want early-stage equity upside, and thrive in fast-moving environments.

What you'll be doing:

• Own systems end-to-end: Scope, build, ship, and iterate on backend services and infrastructure that power our core product.
• Build scalable infrastructure for AI agent systems, dialer infrastructure, and intelligent pipelines that handle thousands of concurrent operations.
• Design and implement core backend systems including APIs, databases, event processing, and real-time data pipelines that support the product.
• Collaborate with frontend engineers and product leadership to translate customer needs into technical architecture and implementation.
• Own reliability and performance: Optimise systems for speed, scalability, and robustness as the user base grows.
• Contribute to technical direction and engineering standards, helping shape how we approach problems and build systems.
• Ship regularly and iterate: Move fast, gather feedback from real users, and continuously improve what you build.
• Work on systems at scale: Build the dialer infrastructure, agent systems, intelligence pipelines, and data processing engines that only a few companies have needed to construct.

What we're looking for:

• Strong technical foundation: You've built complex systems at scale - whether at a top-tier tech company, in a startup, or through ambitious projects. Proof of building something significant matters more than pedigree.
• Strong backend fundamentals: Deep knowledge of data structures, algorithms, system design, and performance trade-offs.
• Startup DNA: Comfort working in a small team, wearing multiple hats, and moving at speed without heavy process.
• AI/LLM experience (a plus): Experience building with AI agents, RAG systems, or LLM-powered features is valuable but not required.
• End-to-end ownership mindset: You've shipped something meaningful on your own—a project, open source tool, or business—and you drive work from conception to production.
• Modern backend fundamentals: Comfortable with modern backend languages and frameworks, plus exposure to databases and infrastructure tooling. Strong fundamentals matter more than a specific language.
• Problem-solving orientation: You think systematically about complex problems and make pragmatic decisions about trade-offs.
• Collaborative mindset: You enjoy working closely with small, ambitious teams and can communicate ideas clearly with engineers and non-technical stakeholders.

What you'll need:

• Professional software engineering experience: 3+ years for mid-level roles, 5+ years for senior roles.
• Strong backend and full-stack web development skills: Comfortable building scalable servers, APIs, and databases.
• Computer science fundamentals: Solid grasp of data structures, algorithms, system design, and performance optimization.
• TypeScript/JavaScript or equivalent: Production experience with modern backend languages and frameworks.
• Database and infrastructure knowledge: Experience designing schemas, optimizing queries, and working with modern databases (SQL/NoSQL).
• Ability to work in an early-stage environment: Comfort with ambiguity, evolving priorities, and hands-on technical work.
• Office-first culture: Based in London, 5 days per week. We believe in-person collaboration drives better decisions and faster iteration.
• Sometimes late hours required: Critical customer operations occasionally require availability outside standard hours—a sign you're working on something that matters.
• CS degree or equivalent experience: Academic foundation in computer science or equivalent self-taught depth.
• Meaningful equity: Early-stage equity participation reflecting your impact and contribution to the company's growth.
• Real impact from day one: Your code directly generates business outcomes. No busywork, no bloat.
• Architectural ownership: Own systems end-to-end, from design through production and iteration.
• Work on rare systems: Build infrastructure that most engineers have only read about—dialer systems, AI agents, real-time intelligence pipelines.
• Small, senior team leverage: A handful of engineers with significant autonomy shipping systems that power outcomes for hundreds of customers.
• Early-stage upside: Join at a critical growth inflection point with product-market fit and clear trajectory.
• Proven business model: Work on a product that customers actively pay for and rely on—the most motivating kind of problem to solve.
• Direct relationship with leadership: Close collaboration with founders and product leadership means your ideas shape the direction.
• Opportunity to grow: As the company scales, so do the opportunities for technical depth, mentorship, and leadership.