Principal or Lead C#/.NET Engineer | Applicant Must Be Currently Local to Hamilton, NJ | Relocation Not Allowed

NOTE: APPLICANT MUST BE ON OUR W2 OR 1099. C2C IS ALLOWED IF OWN CORPORATION ONLY. NOT ACCEPTING SUB-VENDORS. APPLICANT MUST BE CURRENTLY LOCAL TO HAMILTON, NJ AT THE TIME OF SUBMISSION. RELOCATION IS NOT ALLOWED. 

Role: Principal or Lead C#/.NET Engineer

Location: Hamilton, NJ – Hybrid

Duration: 12 Months

Interview: In-Person

Work Arrangement: Hybrid - Will start 100% on site for 30 days & move to hybrid 3 days onsite 2 days remote

Short Description:

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.

Complete Description:

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.

Key Responsibilities:

C# / .NET Engineering:

·       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, AsNoTracking, 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, PostgreSQL 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 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

·       Strong relational database skills; PostgreSQL strongly preferred (Oracle/SQL Server acceptable) — schema design, indexing, query tuning, stored procedures

·       ASP.NET 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

Skill                                   Required / Desired                                 Amount of Experience

·       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 Experience. – Required – 10 Years

·       Solid software design: SOLID, design patterns, domain modeling, layered/clean architecture, dependency injection. – Required – 5 Years

·       Angular 17+, Typescript and Node.js experience. – Required – 5 Years

·       Strong relational database skills; PostgreSQL strongly preferred (Oracle/SQL Server acceptable) — schema design, indexing, query tuning, stored procedure. – 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