NJDHS - DFD Principal C#/.NET Engineer – Mainframe Modernization & EF Core (811318)

Rulesys Technologies Inc; Hamilton, Northern (NJ, KY); Hybrid; USD 124,000 - 207,000; Full time

Benefits offered by this job

Hybrid work arrangement

Job summary

NJDHS in New Jersey seeks a Lead C#/.NET Engineer to modernize a large mainframe-derived benefits system, converting COBOL/JCL to C#, and migrating data to PostgreSQL on AWS. You will define EF Core data models, APIs, and CI/CD processes while preserving exact business logic and performance within nightly batch windows.

The role combines leadership with hands-on development, ensuring correctness, scalability, and maintainability of critical government benefits software.

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
• 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
• Legacy modernization experience or mainframe knowledge is a plus

Responsibilities

• Refactor COBOL-derived C# into idiomatic, maintainable .NET with clean OO design
• Work in .NET Core/.NET latest; apply modern C# features (LINQ, async/await, records)
• Design and implement service layers, domain models, and APIs (ASP.NET Core Web API) for the Angular UI
• Refactor legacy batch/procedural logic into maintainable .NET; ensure correct decimal/financial arithmetic
• Optimize performance to meet nightly batch windows and SLAs

Skills

C#/.NET

EF Core

PostgreSQL

AWS

REST API

Angular

Unit tests

CI/CD

Git

TDD

Performance

Mainframe modernization

Tools

Npgsql

SQL

Job description

NJDHS - DFD Principal C#/.NET Engineer – Mainframe Modernization & EF Core (811318)

Acknowledgement

Candidates must agree to the following terms before applying:

• This is a contract role; visa sponsorship is not provided.
• You have not applied for this position through any other agency or recruiter.
• Candidates must work directly on a C2C (Corp-to-Corp) basis.

Req. ID 811318

Requisition Class Developer N2

Region Name State of New Jersey

Title/Role NJDHS - DFD Principal C#/.NET Engineer – Mainframe Modernization & EF Core (811318)

Region Description State of New Jersey

Req. Status Open

No. of Openings 1

Start Date Oct 1, 2026

End Date Jun 30, 2027

Agency Interview Type In Person Only

Priority Normal

Standard Work Week (In Hours) 40

Work Arrangement Hybrid

Work Location Mercer County

Client NJDHS, Division of Family Development

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

Note: This is a Hybrid position - 100% On-Site for the first 30 days, then 3 Days On-Site, 2 Days Remote

Interviews are in person only.

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. 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

• 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-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
• 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
• 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 / Desired Skills

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 procedures 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