Java+C# - Development Lead

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.