C#​/.NET Engineer

• Deep expertise in C# and the .NET platform (.NET Framework and .NET 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

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.

We are looking for a C#/.NET Engineer to lead the modernization of a mission-critical legacy benefits system hosted on AWS Cloud.

• Refactor machine-converted, COBOL-derived C# into idiomatic, maintainable .NET — meaningful naming, proper OO/domain design, separation of concerns, dependency injection
• Work in .NET (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 (ASP.NET Core Web API) that back the Angular UI
• Refactor legacy batch/procedural logic (converted from COBOL/JCL) into maintainable, testable .NET; 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, 4,024+ fields)
  • Optimize EF Core queries (eager/lazy/explicit loading, projection, As No Tracking , compiled queries, batching) to avoid N+1 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…