Founding Engineer Python API LLM - Start-up

Client Server Ltd.; Greater London; Hybrid; GBP 90,000 - 115,000; Full time

Benefits offered by this job

Equity

Job summary

Client Server Ltd. in London is seeking a Founding Engineer to own the design and development of scalable, cloud-native Python applications for an AI start-up serving regulated industries.

You will work across the full SDLC, from architecture and backend services through to frontend, CI/CD, and deployment on Azure, with hybrid work between London and Cambridge and occasional WFH. Candidates should have strong Python skills, experience with RESTful APIs (FastAPI), TypeScript/React, and a startup

Qualifications

• Strong Python development skills.
• Experience with RESTful APIs (FastAPI).
• Frontend basics in TypeScript/React desirable.
• Experience with LLMs and agentic AI.
• Degree in Computer Science or closely related discipline, 2.1+.

Responsibilities

• Own the design and development of scalable, cloud-native applications.
• Work across the full software development lifecycle: architecture to deployment.
• Collaborate across backend and frontend, CI/CD and Azure deployment.
• Influence technical direction and engineering practices.

Skills

Python

RESTful APIs

TypeScript

React

LLMs

Entrepreneurial spirit

Ownership

Communication

Education

BSc in Computer Science or closely related

Top tier university background

Tools

FastAPI

Azure

HTML5

CSS3

Job description

London, Greater London | £90k - £115k per year

Founding Engineer / Developer (Python API LLM) to £115k

Do you have advanced Python skills combined with tech start-up experience?

You could be progressing your career at a fast growing AI start-up as a Founding Engineer, building technology that is transforming compliance and operational efficiency across the NHS and wider regulated industries. With strong backing and ambitious growth plans, you'll have the chance to make a genuine impact while working alongside experienced founders in a highly collaborative environment.

As a Founding Engineer, you'll take ownership of the design and development of scalable, cloud-native applications, working across the full software development lifecycle, from architecture and backend services through to frontend development, CI/CD and deployment on Azure.

You'll collaborate closely with the founding team to influence technical direction, solve complex engineering challenges and establish the engineering practices that will underpin the company's future growth.

You'll work primarily with Python and TypeScript, leveraging AI technologies to build innovative products that solve real world problems. This is a hands‑on role with plenty of autonomy, where you'll have a direct influence on product decisions, architecture and engineering culture.

Location / WFH:

You'll join the team in London two days a week, with one day a week in Cambridge too (expenses covered) and flexibility to work from home.

About you:

• You enjoy taking ownership and can build software from scratch and iterate quickly
• You have strong technical skills, primarily with Python
• You have experience with RESTful APIs (they use FastAPI); TypeScript, React and other web technologies such as HTML5, CSS3 would be of benefit
• You have experience with LLMs and agentic AI, like to get your hands dirty and have a proactive entrepreneurial spirit
• You're curious by nature, happy to learn and pick up new things
• You're keen to work in a start-up environment, comfortable with unstructured environments
• You're collaborative with great communication skills
• You are degree educated, minimum 2.1 at BSc from a top tier university, Computer Science or closely related discipline preferred, likely to have studied to MSc / PhD

What's in it for you:

• Salary to £115k
• Equity
• Impactful role with excellent career growth opportunities