Full-Stack Engineer (Founding) (up to £130k)

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

Job summary

Dex is partnering with a security-focused startup to hire a software engineer who will own the full stack from data ingestion to the user interface, including the evaluation that proves correctness. The role focuses on a platform that answers security questions with evidence and adapts as environments shift, using Python on the backend and React on the frontend.

You will work directly with the founder and customers, tackle complex, question-first problems, and ship end-to-end solutions across

Qualifications

• Proven experience with full-stack development.
• Experience with Python on backend and React on frontend.
• Track record shipping LL-powered products.
• Able to work in an early-stage startup environment.

Responsibilities

• Own the full stack, from data ingestion and modeling to user-facing interfaces and the evaluation proving correctness.
• Tackle complex, question-first problems: determine the evidence needed to settle a security flaw, then build the systems to gather it.
• Navigate vast, dynamic customer environments that defy simple modeling, ensuring answers remain accurate as conditions change.
• Deliver end-to-end solutions, like identifying and removing unwanted packages across an entire customer estate.
• Engage directly with customers to understand their problems and validate your solutions.

Skills

Python

React

LLM products

Full-stack

Customer-facing

Job description

This role is with one of Dex's trusted partner companies. We work closely with their teams to truly understand their culture, goals, and what they're looking for, so we can match you with the right opportunity and give you context about the role before you commit to a process.

The role

Security teams waste cycles re-investigating the same vulnerabilities. This platform answers security questions once, provides the evidence, and keeps that answer true as environments shift. It then hands the root cause to coding agents, stopping the same class of bug from shipping again. The company is backed by leading VCs and already works with early customers.

You'll join a small, founding team, owning the entire path from data model to the UI that makes an answer readable, including the evaluation that proves it's right. This isn't just building features; it's solving a moving target problem: answering complex security questions across estates too large for a single model, where facts constantly change. You'll work directly with the founder and customers, shipping Python and Prefect on the backend, React on the frontend.

The work

• Own the full stack, from data ingestion and modeling to user-facing interfaces and the evaluation proving correctness.
• Tackle complex, question-first problems: determine the evidence needed to settle a security flaw, then build the systems to gather it.
• Navigate vast, dynamic customer environments that defy simple modeling, ensuring answers remain accurate as conditions change.
• Deliver end-to-end solutions, like identifying and removing unwanted packages across an entire customer estate.
• Engage directly with customers to understand their problems and validate your solutions.

What You Bring

• Strong engineering fundamentals: databases, testing, and operating production systems. Python is core; React is a significant plus.
• Experience shipping LLM-powered products, with a clear understanding of how to measure and prove their improvement.
• The ability to build and ship effectively in a lean, early-stage environment, moving fluidly between backend, frontend, and problem-solving.
• A track record of owning customer problems from initial conversation through to production deployment.
• Enough experience to trust your judgment and adapt your approach, valuing variety over rigid methodologies.