Senior C#/.NET Engineer — EF Core & Cloud Modernization

Mbi Llc; Hamilton (NJ); On-site; USD 140,000 - 190,000; Full time

Job summary

Mbi Llc is seeking a Lead/Principal C#/.NET engineer to own refactoring of a COBOL-derived codebase into clean, production-grade C#/.NET. You will define the data-access architecture using EF Core against PostgreSQL and set engineering standards for the team while ensuring functional equivalence to the legacy system.

You will lead the modernization of a large, mission-critical benefits system for NJ families, focusing on correctness, nightly batch performance, and maintainability within a

Qualifications

• 12-15 years of professional C#/.NET software engineering with senior/lead responsibilities.
• Deep expertise in C# and the .NET platform, including async programming and memory/performance optimization.
• Expert-level EF Core: modeling, migrations, queries, transactions and concurrency.
• Strong relational database skills; PostgreSQL strongly preferred; Oracle/SQL Server acceptable.

Responsibilities

• Refactor COBOL-derived C# into idiomatic, maintainable .NET with good OO design.
• Design and implement service layers, domain models, and APIs to back the UI.
• Own data-access architecture using EF Core against PostgreSQL and optimize queries.
• Define and enforce coding standards and refactoring guidelines for the team.
• Ensure functional equivalence with legacy system and build tests (unit/integration).
• Deliver iteratively within Scrum and participate in CI/CD pipelines.

Skills

C#/.NET

.NET Core / .NET 6/7/8+

EF Core / LINQ / async

REST API design

Git

CI/CD

AWS

PostgreSQL

Performance optimization

Npgsql

Tools

ASP.NET Core

PostgreSQL

Job description

Mbi Llc is seeking a Lead/Principal C#/.NET engineer to own refactoring of a COBOL-derived codebase into clean, production-grade C#/.NET. You will define the data-access architecture using EF Core against PostgreSQL and set engineering standards for the team while ensuring functional equivalence to the legacy system.

You will lead the modernization of a large, mission-critical benefits system for NJ families, focusing on correctness, nightly batch performance, and maintainability within a