About the job
Principal Software Engineer wanted by a well-funded, early-stage company building a customer-facing AI software platform.
Our client recently completed their Series A round and are now making several senior engineering hires as they continue developing the product and expanding its use among customers.
This is first and foremost a software engineering position. They need someone who can build reliable products across backend services, integrations, infrastructure and, where required, the frontend.
You will also need genuine experience building LLM or agentic systems that have progressed beyond prototypes and into production.
The main stack is Python, FastAPI and PostgreSQL, with TypeScript and Next.js on the frontend. The platform runs on GCP using Kubernetes.
You will be responsible for:
- Building and shipping core product features across Python and cloud infrastructure
- Developing reliable asynchronous Python services
- Building LLM and agent-based functionality into the product
- Designing event-driven systems and third-party integrations
- Working directly with customers to understand problems, scope solutions and deliver working software
- Deciding when an MVP is appropriate and when something needs to be built for longer-term scale
- Maintaining strong standards across testing, documentation, security and reliability
- Helping shape the technical direction of the product as the engineering team grows
They are looking for:
- Excellent Python development experience, including asynchronous and concurrent services
- Experience designing, building and shipping production software
- Hands-on experience building LLM applications or agentic systems used by customers
- Experience with cloud infrastructure, Kubernetes, serverless platforms or distributed systems
- Early-stage startup experience, ideally at Series A or earlier
- The ability to work directly with non-technical customers and take ownership from initial requirement through to delivery
- TypeScript, customer-facing integrations and event-driven architecture would all be useful, but they are not essential.
This would not suit someone whose experience is predominantly academic machine learning, data science or AI strategy. They need an engineer who still writes production code and is comfortable owning difficult technical problems from start to finish.
The salary is £150,000 to £250,000 plus equity, depending on experience.
Please note that the role is based in the company’s central London office five days per week.
Permanent, Central London, Onsite
£150,000 - £250,000 plus equity
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