Lead C#.NET Engineer

Sr/Lead C#/.NET Engineer

Location: Hamilton NJ (Hybrid)

Position Type: Contract

In Person Only

Lead/Principal C#/.NET Engineer with expert-level Entity Framework Core experience to lead the modernization of a mission-critical legacy benefits system hosted on AWS Cloud.

Position Summary:

We are modernizing a large mission-critical Honeywell Bull mainframe benefits system (FAMIS) converting 1.5M lines of COBOL and 160K lines of JCL to C#/.NET migrating an IDS-II hierarchical database to PostgreSQL and deploying on AWS. Converted code is delivered by an automated modernization vendor in an as-is state. This Lead/Principal role owns the refactoring of that converted code into clean maintainable high-performance production-grade C#/.NET defines the data-access architecture using Entity Framework Core against PostgreSQL sets engineering standards for the team and safeguards functional equivalence to the legacy system. This is a benefits system serving NJ families correctness performance within the nightly batch window and maintainability are paramount.

Required skills:

• C# Programming Experience Required 10 Years
• .NET Core / .NET 6/7/8/10 Experience Required 10 Years
• .NET REST/WEB API Development Experience Required 5 Years
• Entity Framework Core and LINQ and async/await patterns Experince Required 10 Years
• Solid software design: SOLID design patterns domain modeling layered/clean architecture dependency injection Required 5 Years
• Angular 17 Typescript and experience Required 5 Years
• Strong relational database skills; PostgreSQL strongly preferred (Oracle/SQL Server acceptable) schema design indexing query tuning stored proc Required 5 Years
• unit/integration/regression testing frameworks; TDD/mocking Required 5 Years
• Git and static code analysis (SonarQube) Required 5 Years
• Docker containerization and CI/CD pipeline experience (AWS CODEPIPELINE OR GitHub Actions) Required 3 Years
• AWS cloud native applications (S3 SNS SQS ECS RDS EC2 Lambda) Required 3 Years

Responsibilities:

• C# / .NET Engineering
• Refactor machine-converted COBOL-derived C# into idiomatic meaningful naming proper OO/domain design separation of concerns dependency injection
• Work (Core) / .NET (latest version); apply modern C# language features (LINQ async/await records pattern matching nullable reference types generics)
• Design and implement service layers domain models and APIs ( Core Web API) that back the Angular UI
• Refactor legacy batch/procedural logic (converted from COBOL/JCL) into maintainable ; handle exact decimal/financial arithmetic (decimal rounding rules) to preserve benefit-calculation correctness
• Optimize performance to meet the nightly batch window (profiling memory management async I/O parallelism where safe)
• Entity Framework / Data Layer
• Own the data-access architecture using Entity Framework Core against PostgreSQL (Npgsql provider)
• Refactor the auto-generated/converted data-access layer into a clean performant EF Core model
• Design entity models DbContext configuration Fluent API mappings relationships keys and indexes reflecting the IDS-II PostgreSQL schema (168 tables 4024 fields)
• Optimize EF Core queries (eager/lazy/explicit loading projection AsNoTracking compiled queries batching) to avoid N1 and meet performance SLAs on high-volume batch operations
• Manage EF Core migrations concurrency handling transactions and connection resiliency
• Map legacy data types and semantics correctly (packed decimals fixed-width EBCDIC-origin data condition codes) to PostgreSQL/EF types without behavioral drift
• Contribute to the COBOL-field PostgreSQL-column business-term data dictionary
• Technical Leadership
• Define and enforce C#/.NET coding standards architecture patterns and refactoring guidelines for the engineering team
• Serve as senior technical authority on the converted codebase; make cross-cutting design decisions
• Mentor mid/junior C# developers; perform code reviews; drive engineering quality
• Partner with the Technical Manager/Architect on target architecture and the refactoring strategy
• Quality Testing & Delivery
• Ensure functional equivalence: build unit and regression tests (xUnit/NUnit Moq) to validate refactored code against the legacy baseline; fix FET-surfaced defects
• Integrate with CI/CD (AWS CodeBuild/CodePipeline) enforce quality/security gates (SonarQube static analysis secure coding/OWASP)
• Collaborate with FAMIS SMEs to preserve business logic (eligibility benefit calculation payments EBT)
• Deliver incrementally within Scrum; document design and decisions
• Required Qualifications
• 12-15 years of professional C#/.NET software engineering including senior/lead responsibilities
• Deep expertise in C# and platform (.NET Framework Core / .NET 6/8) including async programming memory/performance optimization and modern language features
• Expert-level Entity Framework / EF Core: entity modeling Fluent API migrations query optimization transactions concurrency provider-specific behavior
• Strong relational database skills; PostgreSQL strongly preferred (Oracle/SQL Server acceptable) schema design indexing query tuning stored procedures
• Core Web API design (REST) for front-end integration
• Solid software design: SOLID design patterns domain modeling layered/clean architecture dependency injection
• Testing discipline: unit/integration/regression testing frameworks; TDD/mocking
• Git CI/CD and static code analysis (SonarQube)
• Proven ability to read reason about and safely refactor large unfamiliar codebases
• Exceptional attention to correctness financial/benefit calculation accuracy
• Preferred / Nice to Have
• Legacy modernization experience COBOL-to-C#/Java conversion mainframe migration or automated-transformation tooling
• Understanding of mainframe concepts (COBOL JCL batch processing hierarchical/CODASYL databases like IDS-II/IMS) to reason about source behavior
• High-volume batch processing performance tuning
• AWS experience (ECS/EKS Lambda RDS for PostgreSQL S3 CloudWatch IaC/CloudFormation)
• Experience integrating with enterprise job schedulers (Stonebranch Control-M CA7)
• Government / benefits / healthcare or other regulated high-correctness domains
• Npgsql specifics EF Core performance internals or ORM migration experience
• Success in the First 90 Days
• Establish the C#/.NET and EF Core standards patterns and reference implementation the team will follow
• Refactor a representative set of converted programs (including a benefit-calculation and a batch program) to clean tested performant C# validated against the legacy baseline
• Define the EF Core data-access approach against PostgreSQL including query-performance guardrails for batch workloads
• Mentor the team and set the code-review/quality bar

Required Skills:

TypescriptAngular 6/7/8/10AWSGitPostgreSQL