Platform Engineer - AI Security & API Platform

Refractal; Greater London; On-site; GBP 60,000 - 115,000; Full time

Benefits offered by this job

Competitive salary

Equity

Performance-linked bonus

Influence over product & architecture

London-based, in-person work

UK visa sponsorship

Job summary

Refractal, a London-based AI security company, is hiring a strong backend engineer to own the core product platform APIs and SDKs. You will build enforcement services with FastAPI, design robust authentication and multi-tenant access, and create data interfaces and real-time streams for customers.

You will work directly with the founders and early customers to translate security needs into reliable platform interfaces and operator tools, with visibility into testing, deployment, and

Qualifications

• Strong backend experience with HTTP APIs and Python.
• Experience with FastAPI.
• Experience with observability and relational databases.
• Knowledge of multi-tenant authentication and API security.
• Ability to work independently on complex customer problems.
• Good JavaScript and React skills.

Responsibilities

• Own stable, versioned platform APIs and SDKs, including client interfaces, compatibility rules, documentation, and examples.
• Build FastAPI services for enforcement decisions, evidence, policies, and red-team results.
• Design authentication, sessions, API keys, authorisation, and multi-tenant isolation.
• Build data and event interfaces, real-time streams, and a tamper-evident audit ledger.
• Create customer onboarding, policy integration, and operator dashboard workflows.
• Own testing and deployment across API compatibility, browser smoke tests, Cloud Run, and Cloud SQL.

Skills

Python

FastAPI

HTTP APIs

Observability

Relational databases

API design

Authentication

JavaScript

React

Independent work

Tools

Cloud Run

Cloud SQL

Job description

Refractal, a London-based AI security company, is hiring a strong backend engineer to own the core product platform APIs and SDKs. You will build enforcement services with FastAPI, design robust authentication and multi-tenant access, and create data interfaces and real-time streams for customers.

You will work directly with the founders and early customers to translate security needs into reliable platform interfaces and operator tools, with visibility into testing, deployment, and