Senior C#/.NET Engineer - Hybrid Cloud Modernization

CAI; New Jersey; Hybrid; USD 80,000 - 85,000; Full time

Benefits offered by this job

Medical, dental, and vision insurance

401k retirement plan

Paid time off

Job summary

CAI is looking for a highly skilled C#/.NET Engineer to lead modernization of a mission-critical legacy benefits system hosted on AWS. This full-time, hybrid role is based in Hamilton, NJ.

You will refactor COBOL-derived code to idiomatic .NET, design EF Core data access, implement REST APIs with ASP.NET Core, and collaborate with SMEs to preserve business logic and accuracy in calculations. Strong leadership and testing discipline 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).
• 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 machine-converted COBOL-derived C# into idiomatic, maintainable .NET with proper OO design.
• Work in .NET Core / .NET latest, using LINQ, async/await, and modern features.
• Design and implement service layers, domain models, and APIs that back the Angular UI.
• Refactor legacy logic into maintainable, testable code; preserve exact decimal arithmetic.
• Optimize performance to meet nightly batch windows; profile and parallelize where safe.
• Own EF Core data layer, migrations, and performance tuning; map to PostgreSQL schema.
• Lead technical decisions, enforce coding standards, and mentor developers.
• Ensure unit/regression tests and CI/CD integration; collaborate with SMEs.

Skills

C#/.NET engineering

Entity Framework Core

ASP.NET Core Web API

SQL/PostgreSQL

Async programming

SOLID / design patterns

Unit / integration testing

CI/CD

Performance optimization

Dependency injection

Domain modeling

Mentoring / leadership

Tools

Npgsql

AWS (ECS/EKS, Lambda, RDS)

Git

Job description

CAI is looking for a highly skilled C#/.NET Engineer to lead modernization of a mission-critical legacy benefits system hosted on AWS. This full-time, hybrid role is based in Hamilton, NJ.

You will refactor COBOL-derived code to idiomatic .NET, design EF Core data access, implement REST APIs with ASP.NET Core, and collaborate with SMEs to preserve business logic and accuracy in calculations. Strong leadership and testing discipline required.