Senior Staff Software Engineer

Staff Software Engineer (AI Voice Platform) | London, UK

A Y Combinator-backed, venture-funded startup building AI voice agents for trades and field service businesses (plumbing, electrical, HVAC, facilities) is hiring a Staff Software Engineer to help close out its founding engineering team. The company recently closed a Series A led by a well-known venture fund, giving it strong runway to scale a product that's already automating scheduling, invoicing, and emergency call handling for fleet-based service companies.

The Role

You'll be one of the last founding-level engineering hires, working across the full stack to build and ship core product features: backend services, event-driven systems, cloud infrastructure, and third-party integrations. This isn't a maintain-what-exists role. You'll own outcomes end to end, working directly with customers to scope problems and ship solutions, deciding when to move fast with a scrappy MVP and when to invest in durable infrastructure.

Key Responsibilities

• Build and ship core product features across the stack (backend, frontend, cloud infra, event-driven systems, integrations)
• Own the full lifecycle of features: work directly with customers to understand needs, scope solutions, and deliver outcomes
• Balance speed and durability, knowing when to hack together an MVP and when to build scalable foundations
• Champion engineering best practices (testing, documentation, reliability, security) and help raise the bar across the team

Your Future at the Firm

As one of the final founding-level hires, you'll have outsized influence over technical direction and product architecture as the company scales past its early team. Early engineers at this stage typically move quickly into more senior scope as the org grows, with real ownership over the systems they build rather than a narrow ticket queue.

Who You Are

You're a builder who has shipped AI products end to end, not just experimented with them, and you're comfortable working directly with non-technical customers to turn ambiguous problems into scoped solutions. You thrive in an early-stage environment where the work isn't fully defined yet and you're expected to help define it.

Required Qualifications

• 5-10 years of experience in full-stack software engineering, backend-leaning
• Hands-on experience building and shipping AI products end to end, including agentic systems (not just general ML/data science background)
• Strong async Python experience: async coroutines, httpx, AsyncOpenAI, and production-grade error handling in async contexts
• Experience with modern cloud infrastructure (Kubernetes, serverless, distributed systems)
• Ability to scope and deliver solutions directly with non-technical customers
• Must be able to work in person, 5 days a week, in London

Preferred Experience

• Early-stage startup experience (Series A or earlier)
• Experience with voice AI, event-driven systems, or CRM integrations
• CS degree

Compensation

£150,000 to £250,000 base, plus competitive equity. Visa sponsorship available for the right candidate.

Apply now to be considered for this opportunity.

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