Senior Python Engineer (AI Startup) (C0BE438)

Referment; Greater London; On-site; GBP 70,000 - 120,000; Full time

Benefits offered by this job

Competitive salary

Meaningful equity

Direct access to founders

Early engineering hire

High ownership from day one

Job summary

Referment, partnering with a venture-backed AI startup, seeks an exceptional engineer to build the next generation of AI-powered cybersecurity products. You will work directly with the founders and own features from problem to production.

You'll design complex backend architectures, ship React interfaces, build internal developer tools, and help shape product and engineering culture.

Qualifications

• Strong Python backend fundamentals and modern frameworks.
• Experience across backend, frontend, and infrastructure.
• Verifiable OSS or active GitHub contributions encouraged.

Responsibilities

• Design and own end-to-end features from problem to production.
• Build complex backend architecture and systems.
• Ship React interfaces and internal developer tools.
• Improve databases and handle systems programming tasks.
• Debug production issues and deploy continuously.
• Contribute to product and engineering culture.

Skills

Python backend fundamentals

FastAPI/Django/Flask

React frontend experience

End-to-end product ownership

Startup mentality

3–6 years engineering depth

Tools

FastAPI

Django

Flask

React

Job description

Some engineers enjoy writing code. Others can't stop building.

If you've been programming since you were a teenager, spend your evenings experimenting with new technology, and get genuine satisfaction from shipping products, this role was written for you.

Referment is partnering with a venture-backed AI startup looking for one exceptional engineer to help build the next generation of AI-powered cybersecurity products.

You'll work directly with the founders and own features from customer problem through to production.

You'll enjoy this role if you…

• Love building more than talking about building
• Prefer shipping software over writing documentation
• Can move between backend, frontend and infrastructure without thinking twice
• Get excited by hard engineering challenges like building compilers, DSLs, or internal developer tools
• Use AI every day, but don't rely on it to think for you
• Enjoy solving messy customer problems instead of perfectly defined tickets

What You'll Be Building

Rather than owning a small corner of a huge codebase, you'll own products end-to-end

• You'll design complex backend architecture and systems.
• Ship React interfaces.
• Build internal developer tools and agentic consoles.
• Improve databases and handle systems programming.
• Debug production and deploy continuously.
• Help shape both the product and the engineering culture.

What We're Looking For

• Deep technical focus on hard engineering and complex backend architecture
• Strong Python backend fundamentals with high-level application of tools like FastAPI, Django, or Flask
• Senior-level technical sophistication and the ability to move beyond routine maintenance tasks
• Verifiable track record of technical contributions and honest project claims (e.g. active GitHub or OSS presence)
• React experience or willingness to work across the frontend
• Startup mentality with genuine product ownership
• Around 3-6 years' experience with a focus on engineering depth

Extra points for experience with:

• Founding or leadership roles (e.g. Co-Founder or CTO)
• Building internal developer tools, DSLs, or compilers
• Multi-language proficiency (e.g. Go, C, or Rust)
• Cybersecurity
• Workflow orchestration (Prefect, Airflow)
• High-growth SaaS

This probably isn't for you if…

• Your focus is primarily on product management or innovation titles rather than hands-on engineering
• You consider routine infrastructure maintenance to be your core focus area
• You need detailed specs before starting work
• You only enjoy one part of the stack
• You avoid production responsibility
• You're looking for a comfortable corporate engineering role
• You're currently splitting your attention with another startup

Why join?

• Competitive salary
• Meaningful equity
• One of the first engineering hires
• Direct access to the founders
• Huge ownership from day one
• Build products that customers actually use

#Referment