Senior C#/.NET Engineer — Legacy Modernization Lead

CAI; New Jersey; Hybrid; USD 83,000 - 90,000; Full time

Job summary

CAI is seeking a highly experienced C#/.NET Engineer to modernize a mission-critical legacy benefits system hosted on AWS. The role is full-time with a hybrid work model in Hamilton, NJ, and demands senior leadership on a complex codebase.

You will refactor COBOL-derived code, design robust APIs, and mentor junior developers. The ideal candidate has deep C#/.NET expertise, EF Core mastery, PostgreSQL experience, and strong testing, CI/CD, and performance optimization skills to ensure accuracy in

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

Responsibilities

• Refactor legacy COBOL‑derived code into idiomatic C#/.NET with proper OO design.
• Design and implement service layers, domain models, and APIs backing the Angular UI.
• Migrate data access to EF Core against PostgreSQL; optimize queries and migrations.
• Lead architecture decisions and enforce coding standards for the team.
• Mentor developers, conduct code reviews, and contribute to QA and delivery.
• Collaborate on AWS‑based CI/CD pipelines and maintain security gates.

Skills

C#/.NET

Entity Framework Core

ASP.NET Core Web API

LINQ / async

PostgreSQL

AWS Cloud

Unit testing

CI/CD

Tools

AWS CodeBuild/CodePipeline

Job description

CAI is seeking a highly experienced C#/.NET Engineer to modernize a mission-critical legacy benefits system hosted on AWS. The role is full-time with a hybrid work model in Hamilton, NJ, and demands senior leadership on a complex codebase.

You will refactor COBOL-derived code, design robust APIs, and mentor junior developers. The ideal candidate has deep C#/.NET expertise, EF Core mastery, PostgreSQL experience, and strong testing, CI/CD, and performance optimization skills to ensure accuracy in