Lead Python Engineer API LLM

Client Server; Greater London; Hybrid; GBP 40,000 - 70,000; Full time

Job summary

Client Server is hiring a founding engineer to build scalable AI-powered software in a fast-growing UK startup. You will own major backend services, contribute to frontend work, and shape technical direction with the founders in London and Cambridge.

You will work in a hybrid setup, two days in London and one day in Cambridge, with remote options and equity on offer. Strong Python, FastAPI, TypeScript, and AI experience are highly valued.

Qualifications

• Strong Python skills and experience with RESTful APIs (FastAPI).
• Degree in CS or related field, 2.1 or higher; MSc/PhD preferred.
• Experience with TypeScript, React, HTML5 and CSS3 is beneficial.
• Comfortable in a startup, unstructured environment; ownership and independent work.

Responsibilities

• Build scalable, cloud-native applications across the full SDLC.
• Own backend architecture and services, with frontend collaboration.
• Contribute to CI/CD and deployment on Azure, and establish engineering practices.
• Collaborate with founders to influence technical direction and solve engineering challenges.
• Build AI-powered products using agentic AI and LLMs.

Skills

Python

RESTful APIs

TypeScript

React

LLMs

Agentic AI

Ownership

Communication

Startup environment

Education

Bachelor's degree (2.1) in Computer Science or related

Tools

Azure

FastAPI

CI/CD

HTML5

CSS3

Job description

Salary: £40,000 - 70,000 per year

Requirements

• We want strong technical skills, primarily with Python.
• We want experience with RESTful APIs; we use FastAPI.
• Experience with TypeScript, React, and other web technologies such as HTML5 and CSS3 would be beneficial.
• We want experience with LLMs and agentic AI.
• You should enjoy taking ownership and be able to build software from scratch and iterate quickly.
• You should be curious by nature, happy to learn, and able to pick up new things.
• You should be keen to work in a start-up environment and comfortable with unstructured environments.
• You should be collaborative with great communication skills.
• You should be degree educated, minimum 2.1 at BSc from a top tier university, preferably in Computer Science or a closely related discipline; an MSc or PhD is likely.
• Advanced Python skills combined with tech start-up experience are preferred.

Responsibilities

• We will build scalable, cloud-native applications across the full software development lifecycle.
• We will take ownership of architecture and backend services.
• We will contribute to frontend development, CI/CD, and deployment on Azure.
• We will collaborate closely with the founding team to influence technical direction and solve complex engineering challenges.
• We will establish the engineering practices that will underpin the companys future growth.
• We will work primarily with Python and TypeScript.
• We will leverage AI technologies to build innovative products that solve real-world problems.
• We will take a hands-on role with plenty of autonomy and a direct influence on product decisions, architecture, and engineering culture.

Technologies

• Agentic AI
• AI
• Azure
• Backend
• CI/CD
• Cloud
• FastAPI
• Frontend
• HTML5
• Python
• React
• TypeScript
• Web
• API
• LLM

More

We are a fast-growing AI start-up with strong backing and ambitious growth plans, building technology that is transforming compliance and operational efficiency across the NHS and wider regulated industries. This is a founding engineer opportunity working alongside experienced founders in a highly collaborative environment. You will join our team in London two days a week, with one day a week in Cambridge too, with expenses covered, and flexibility to work from home. We offer a salary of up to 115k, equity, and an impactful role with excellent career growth opportunities.

last updated 36 week of 2026