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David Careers

Lead/Principal C#/.NET Engineer

Posted today

mbiHamilton Township (NJ)
Software DevelopersComputer Systems Design Services

SENIORITY

Lead

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About the role

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.
Key Responsibilities: 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 UIRefactor 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) Entity Framework / Data LayerOwn 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-field → PostgreSQL-column → business-term data dictionary Technical Leadership 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 Partner with the Technical Manager/Architect on target architecture and the refactoring strategy Quality, Testing & Delivery 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 (AWS CodeBuild/CodePipeline), enforce quality/security gates (SonarQube, static analysis, secure coding/OWASP) Collaborate with FAMIS SMEs to preserve business logic (eligibility, benefit calculation, payments, EBT) Deliver incrementally within Scrum; document design and decisions
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) — schema design, indexing, query tuning, stored proceduresASP.NET Core Web API design (REST) for front-end integration
  • 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
  • Preferred / Nice to HaveLegacy modernization experience — COBOL-to-C#/Java conversion, mainframe migration, or automated-transformation tooling
  • Understanding of mainframe concepts (COBOL, JCL, batch processing, hierarchical/CODASYL databases like IDS-II/IMS) — to reason about source behavior
  • High-volume batch processing performance tuningAWS experience (ECS/EKS, Lambda, RDS for PostgreSQL, S3, CloudWatch, IaC/Cloud
Formation) Experience integrating with enterprise job schedulers (Stonebranch, Control-M, CA7) Government / benefits / healthcare or other regulated, high-correctness domains Npgsql specifics, EF Core performance internals, or ORM migration experience Success in the First 90 Days Establish the C#/.NET and EF Core standards, patterns, and reference implementation the team will follow Refactor a representative set of converted programs (including a benefit-calculation and a batch program) to clean, tested, performant C# validated against the legacy baseline Define the EF Core data-access approach against PostgreSQL, including query-performance guardrails for batch workloads Mentor the team and set the code-review/quality bar Fill the skill matrix below: SkillAmountCandidate's No. of years of experienceC# Programming ExperienceRequired10.NET Core / .NET 6/7/8/10 ExperienceRequired10Required5Entity Framework Core and LINQ and async/await patterns Experince Required10Required5Angular 17+, Typescript and Node.js experience Required5Strong relational database skills; PostgreSQL strongly preferred (Oracle/SQL Server acceptable) — schema design, indexing, query tuning, stored procedure Required5unit/integration/regression testing frameworks; TDD/mocking Required5Git and static code analysis (SonarQube) Required5Docker containerization and CI/CD pipeline experience (AWS CODEPIPELINE OR GitHub Actions) Required3AWS cloud native applications (S3, SNS, SQS, ECS, RDS, EC2, Lambda) Required3

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