Senior C# Backend Engineer in City of London

Senior C# Backend Engineer in City of London

City of London Full-Time On-site
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Senior C# Backend Engineer

Β£550 - Β£650 per day

London 2 days per week onsite

This is an opportunity to join a greenfield platform programme focused on building a modern identity and authorisation capability from the ground up. You will help shape core platform services that will be consumed across a wider ecosystem of AI-native applications, data services, and microservices.

The Company

They are a technology-led organisation investing in a next-generation platform designed to support complex enterprise-scale products and services. The programme is in its early stages, giving contractors the opportunity to influence architecture, engineering standards, and platform capabilities. The project is expected to be a long-term initiative, with initial contractors playing a key role in its evolution and future growth.

The Role and Deliverables

  • Develop and maintain authorisation SDKs, Policy APIs, identity services, and authorisation microservices.
  • Design and implement secure identity and access management capabilities using OAuth2, JWT, and OIDC standards.
  • Build authorisation models including RBAC, ReBAC, ACL, policy evaluation, delegated administration, and permission inheritance.
  • Develop integrations with API Gateway, AI Gateway, Kubernetes, and Service Mesh technologies.
  • Contribute to distributed systems design, graph-based relationship modelling, and scalable microservices architecture.
  • Create automated tests, authorisation regression suites, and performance testing frameworks to ensure platform reliability.

Your Skills & Experience

  • Strong experience developing backend applications using C#/.NET, with Java also considered.
  • Expertise building and supporting REST APIs within microservices-based environments.
  • Strong understanding of identity, authentication, and authorisation concepts.
  • Experience working with OAuth2, JWT, and OpenID Connect.
  • Knowledge of distributed systems and graph modelling principles.
  • Ability to design and develop scalable platform services and developer-facing SDKs.
  • Experience integrating systems with Kubernetes, API Gateway technologies, or Service Mesh environments.
  • Understanding of policy-based access control, RBAC, ReBAC, ACL, or policy-as-code frameworks.
  • Exposure to technologies such as Neo4j, OpenFGA, SpiceDB, OPA, Redis, or Kafka would be beneficial.

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Senior C# Backend Engineer in City of London employer: Harnham - Data & Analytics Recruitment

Join a forward-thinking SaaS organisation in London, where you'll not only lead the Data Engineering function but also play a pivotal role in shaping the future of AI and data solutions. With a strong emphasis on innovation, employee development, and a collaborative work culture, this company offers clear progression opportunities and the chance to work on impactful projects that drive commercial success. Enjoy a supportive environment that values your expertise while you tackle exciting technical challenges and contribute to the growth of a rapidly expanding business.

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Contact Details:

Harnham - Data & Analytics Recruitment Recruitment Team