Security Platform Engineer for AI Safety – London

Refractal; Greater London; On-site; GBP 90,000 - 130,000; Full time

Benefits offered by this job

Visa sponsorship

Job summary

Refractal is seeking a Platform Engineer to own the core product platform from external interface to service and data layers. You will focus on the APIs and SDKs used by customers to connect Refractal to their systems, building FastAPI services, authentication, multi‑tenant isolation, data contracts and event interfaces that enable seamless integrations.

You will also craft onboarding flows, policy integration and operator tools, with a dashboard powering secure, auditable enforcement decisions.

Qualifications

• Strong backend experience with HTTP APIs. Experience with Python and FastAPI, or similar tools, is preferred.
• Experience with observability and tracing systems. You can trace agent actions, tool calls, requests, spans and enforcement decisions across services.
• Experience with relational databases. This should include Postgres or SQLite, SQLAlchemy and database migrations.
• Experience in API design, versioning and compatibility. You can create SDKs, documentation and examples that make integration simple.
• A good understanding of authentication, sessions, API keys, authorisation and multi‑tenant access control.
• Experience with data models, event streams, audit records and error handling.
• The ability to work independently, communicate clearly and take ownership of technically uncertain customer problems.
• External API or SDK ownership from data model to customer use.
• Experience with B2B or enterprise integrations, trust/auditability/compliance importance.
• Experience with data‑dense or real‑time systems like security consoles or SSE.
• Experience with containers, CI/CD and cloud platforms (GCP).
• Experience in AI security or high‑assurance tech fields.
• Open‑source or side projects showing engineering decisions and product judgement.

Responsibilities

• Own the platform API and its SDKs. Define stable, versioned contracts, client interfaces, error behaviour, compatibility rules, documentation and examples.
• Design and build the FastAPI services behind these interfaces. Provide access to enforcement decisions, evidence, policies and red‑team results.
• Own identity and access at the platform layer, including authentication, sessions, API keys, authorisation and multi‑tenant access control.
• Design the platform's data and event interfaces, including read models, requests/spans, real‑time SSE streams and an audit ledger.
• Present security data accurately; avoid missing data or false values in APIs, SDKs and UIs.
• Build customer integration and onboarding flows: tenant setup, policy binding, integrations, sign‑in and API‑key issuance.
• Build the operator dashboard as a client of the platform API (heatmap, trajectories, traces, policy compiler, audit ledger).
• Work directly with customers; translate needs into clear product requirements.
• Define engineering standards for APIs, SDKs, components, tests and customer‑facing quality.

Skills

Python

FastAPI

HTTP APIs

Backend development

Observability

Tracing systems

Relational DB

SQLAlchemy

Auth & multi-tenant

Tools

PostgreSQL

SQLite

SQLAlchemy

GCP Cloud Run

Docker

CI/CD

Job description

Refractal is seeking a Platform Engineer to own the core product platform from external interface to service and data layers. You will focus on the APIs and SDKs used by customers to connect Refractal to their systems, building FastAPI services, authentication, multi‑tenant isolation, data contracts and event interfaces that enable seamless integrations.

You will also craft onboarding flows, policy integration and operator tools, with a dashboard powering secure, auditable enforcement decisions.