Principal or Lead C#​/.NET Engineer | Currently Local NJ | Not Allowed

note: applicant must be on our w2 or 1099. C2c is allowed if own corporation only. Not accepting sub-vendors. Applicant must be currently local to hamilton, nj at the time of submission. Relocation is not allowed.

role: principal or lead c#/.net engineer

location: hamilton, nj – hybrid

duration: 12 months

interview: in-person

work arrangement: hybrid - will start 100% on site for 30 days & move to hybrid 3 days onsite 2 days remote

lead/principal c#/.net engineer with expert-level entity framework core experience to lead the modernization of a mission-critical legacy benefits system hosted on aws cloud.

we are modernizing a large, mission-critical honeywell bull mainframe benefits system (famis) — converting ~1.5m lines of cobol and ~160k lines of jcl to c#/.net, migrating an ids-ii hierarchical database to postgresql, and deploying on aws. Converted code is delivered by an automated modernization vendor in an "as-is" state. This lead/principal role owns the refactoring of that converted code into clean, maintainable, high-performance, production-grade c#/.net,

defines the data-access architecture using entity framework core against postgresql, sets engineering standards for the team, and safeguards functional equivalence to the legacy system. This is a benefits system serving nj families — correctness, performance within the nightly batch window, and maintainability are paramount.

• refactor machine-converted, cobol-derived c# into idiomatic, maintainable .net — meaningful naming, proper oo/domain design, separation of concerns, dependency injection.
• work in .net (core) / .net (latest version); apply modern c# language features (linq, async/await, records, pattern matching, nullable reference types, generics)
• design and implement service layers, domain models, and apis (asp.net core web api) that back the angular ui.
• refactor legacy batch/procedural logic (converted from cobol/jcl) into maintainable, testable .net; handle exact decimal/financial arithmetic (decimal, rounding rules) to preserve benefit-calculation correctness.
• optimize performance to meet the nightly batch window (profiling, memory management, async i/o, parallelism where safe).

• own the data-access architecture using entity framework core against postgresql (npgsql provider).
• refactor the auto-generated/converted data-access layer into a clean, performant ef core model.
• design entity models, dbcontext configuration, fluent api mappings, relationships, keys, and indexes reflecting the ids-ii ? Postgresql schema (168 tables, 4,024+ fields).
• optimize ef core queries (eager/lazy/explicit loading, projection, asnotracking, compiled queries, batching) to avoid n+1 and meet performance slas on high-volume batch operations.
• manage ef core migrations, concurrency handling, transactions, and connection resiliency.
• map legacy data types and semantics correctly (packed decimals, fixed-width, ebcdic-origin data, condition codes) to postgresql/ef types without behavioral drift.
• contribute to the cobol, postgresql business-term data dictionary.

• define and enforce c#/.net coding standards, architecture patterns, and refactoring guidelines for the engineering team.
• serve as senior technical authority on the converted codebase; make cross-cutting design decisions.
• mentor mid/junior c# developers; perform code reviews; drive engineering quality.
• partner with the technical manager/architect on target architecture and the refactoring strategy.

• ensure functional equivalence: build unit and regression tests (xunit/nunit, moq) to validate refactored code against the legacy baseline; fix fet-surfaced defects.
• integrate with ci/cd…