Backend Engineer in London

We are looking for a Senior Backend Engineer with extensive experience in the healthcare domain to join our application modernization team. This role is focused on re-architecting and migrating a mission-critical legacy enterprise application to a modern .NET ecosystem. You will be responsible for building high-performance, secure, and scalable server-side logic that interfaces with existing SQL databases while adhering to strict healthcare regulatory standards.Key Responsibilities Legacy Logic Transformation: Analyze and translate complex business rules from legacy source code into clean, maintainable, and testable .NET services.High-Performance API Development: Design, build, and maintain robust RESTful APIs using .NET 6/8+, ensuring low-latency response times for Angular front-end consumers.Database Engineering: Optimize existing SQL Server structures. You will be responsible for refactoring legacy \”record-based\” data access into efficient set-based operations using Entity Framework Core and Dapper.Healthcare Compliance: Architect data access layers that strictly enforce HIPAA compliance, including row-level security, data masking, and comprehensive audit logging.Integration & Messaging: Implement asynchronous processing and inter-service communication using message brokers (e.g., Azure Service Bus, RabbitMQ) where applicable.Quality Assurance: Lead the implementation of Test-Driven Development (TDD) practices, ensuring high code coverage via unit and integration tests.Required Technical Skills Core Stack: 7+ years of deep expertise in C# and .NET Core / .NET 5+ .Database Mastery: Expert-level SQL Server skills (T-SQL, stored procedures, execution plan analysis, and performance tuning).ORM: Advanced experience with Entity Framework Core (including interceptors and performance optimization).Architecture: Strong mastery of Web API, Microservices, and Clean Architecture (Onion/Hexagonal).Security: Solid understanding of IdentityServer, JWT, and OAuth2 implementation.Industry Experience Requirements Healthcare Domain: Minimum 5+ years of experience developing Healthcare IT products (EMR, PMS, Billing, or Clinical systems).Regulatory Knowledge: Practical experience implementing HIPAA, HITECH, and HL7/FHIR data standards.

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