Senior Backend Engineer

Company: Nelly Works
Apply for the Senior Backend Engineer
Location: London
Job Description:

NB: 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.
  • 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

  • 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.
  • Meaningful equity: Early-stage equity participation reflecting your impact and contribution to the company’s growth.

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Posted: May 18th, 2026