Senior Backend Engineer- London

FDM is a global business and technology consultancy seeking a Senior Backend Engineer with Active SC to work for our client within the Public sector. This is initially a 3 month contract with the potential to extend and will be a hybrid role that will be based in London.

Our client is seeking an experienced backend engineer to join a team delivering a referral capability discovery and technical proof of concept. The project will test how staff and authorised systems can create referrals, keep the relevant business context, notify recipients and track responses across a business support ecosystem. You will build the referral service's backend, APIs and integrations in Python/Django, working with the Technical Architect and Engineering Lead. Your focus will be making referral creation, storage, notifications and status changes reliable, secure and ready to demonstrate. The outcome will be a working demonstrator and supporting evidence to inform a decision on moving to alpha.

Responsibilities

• Implement referral business logic, validation and an agreed state model, recording each transition with its timestamp, actor or system and correlation identifier.
• Design and implement PostgreSQL models and migrations for referrals and event history, storing only justified company identifiers and minimal snapshots.
• Build documented REST/JSON endpoints for authorised referral creation, retrieval and responses, with idempotency, consistent error handling and access controls.
• Integrate the Company Data Layer for company lookup and GOV.UK Notify for transactional email, using contract faithful stubs where dependencies are unavailable.
• Implement the agreed recipient response endpoint and verification controls, keeping email delivery and referral status updates as separate responsibilities.
• Handle retries, duplicates, notification failures and partial failures without any silent loss of referrals.
• Write automated unit, integration and API contract tests, including negative security and failure path cases, and contribute to GitHub Actions checks and peer reviews.
• Add structured logs, correlation identifiers and useful metrics without exposing personal data, and document API usage, local setup and backend support procedures.