Java+C# - Development Lead

HRB; Columbus (OH); On-site; USD 120,000 - 150,000; Full time

Job summary

HRB is seeking a senior developer to bridge Java and C# ecosystems. You will migrate services from Java to C# using AI-assisted first drafts, then refine by hand to align with .NET patterns. You’ll work across the IL4 codebase, ensuring parity and reliable tests.

The role emphasizes deep Java expertise, strong C#/.NET skills, and hands-on migration of production code with automated parity tests.

Qualifications

• 8+ years of production Java experience with recent work.
• 5+ years hands-on C# and .NET Core / .NET 6+ experience.
• Experience migrating between Java and C# and proving parity.
• Both languages shipped in production within the last 2 years.
• Ability to validate equivalence with automated tests, not manual checks.

Responsibilities

• Work across Java and C# code in the IL4 codebase, moving between them as needed.
• Convert Java services to C# / .NET, using AI drafts first, then finish by hand to match patterns.
• Review AI-converted output for correctness, edge cases, and API behavior drift.
• Map Java constructs to .NET equivalents (Spring to ASP.NET Core, JPA/Hibernate to EF, Maven to NuGet).
• Preserve service contracts: REST endpoints, payloads, error handling, and config behavior.
• Write or port tests to prove functional parity before and after migration.

Skills

Java

C#/.NET

Spring Boot

ASP.NET Core

REST APIs

Migration

Tools

Docker

Kubernetes

AWS

Azure

EF / Dapper

NuGet

Job description

About the role

IL4 is natively built on both Java and C#. This role is the true bidirectional profile: a developer who reads and writes both languages fluently and can move between them daily. The work includes converting Java services to C# using AI-assisted conversion as a first pass plus hands-on rework, and working across the existing Java and C#code as the architecture consolidates. This is the hardest of the Crown profiles to fill, so screen tightly.

What you will do

• Work across both Java and C# code in the IL4 codebase, moving between them as the work demands.
• Convert Java services to C# / .NET, using AI-generated first drafts as a starting point and finishing them by hand to the client& C# patterns.
• Review AI-converted output for correctness, missed edge cases, hallucinated APIs, and behavior drift between the Java original and the C# result.
• Map Java constructs to their .NET equivalents (Spring to ASP.NET Core, JPA/Hibernate or DAO/SQL to EF or Dapper, Maven to NuGet).
• Preserve service contracts: REST endpoints, payloads, error handling, and config behave the same after conversion.
• Write or port tests to prove functional parity before and after migration.

Must have qualifications

• Deep, current Java: 8+ years production Java, current within the last 1-2 years. Spring Boot strongly preferred. Can read unfamiliar Java and explain what it does and why.
• Strong C# / .NET: 5+ years hands-on C# and .NET Core / .NET 6+, ASP.NET Core Web APIs, dependency injection, async/await.
• Real migration scars: Has personally converted or re-platformed code between different languages (not just a framework version upgrade inside one language) and can describe what broke and how they proved parity.
• Both languages current: Shipped production code in each within roughly the last two years, not one current and one from a decade ago.
• Parity discipline: Proves equivalence with automated tests, not visual inspection.

Nice to have

• Hands-on use of AI coding tools for conversion or large refactors, with an honest view of where they fail.
• Interest in building the conversion harness: prompt templates, pattern libraries, parity test frameworks.
• Docker/Kubernetes, AWS or Azure, API gateways (Kong), MySQL and SQL Server.