backend developer for a legacy financial system

The role focuses on replacing a critical financial processing function within a large US benefits organization. The legacy function is being separated from a core system into a standalone application, with its behavior reconstructed from historical data, documentation, and expert workshops and validated against historical results.

• Lead discovery with the client's product, business, and technology teams to understand the domain, assess the current architecture, and propose a target technical approach
• Define the team composition and technical roadmap, then lead implementation through build, migration, and production cutover
• Reverse-engineer legacy business rules using database extracts, historical outputs, documentation, and SME interviews
• Design and validate financial logic for contribution processing, weighted allocation across funds, interest recalculation, receivables, period close, and full audit trails
• Own high-volume migration of historical data, including source profiling, transformation, reconciliation, exception handling, and parallel-run validation
• Design integration architecture with feed and API contracts, idempotency, retry and error handling, observability, and cross-system reconciliation
• Run requirements and architecture sessions with technical and non-technical stakeholders, resolve ambiguous business rules, and document technical and business decisions
• Stay hands-on in design, code, and reviews
• Ensure delivery meets requirements for access control, auditability, sensitive data handling, secrets management, deployment controls, and production change management
• Propose the best technology approach based on discovery findings

• Proven experience leading a legacy system replacement, carve-out, or system separation through production cutover, with personal ownership of the replacement design and involvement through migration. Greenfield-only experience is not sufficient
• Strong experience with financial transaction systems involving ledgers or subledgers, allocation across funds or accounts, reconciliation, period close, adjustments, and audit trails in pension, insurance, banking, billing, payroll, claims, or similar domains
• Strong backend architecture experience; .NET is strongly preferred. Candidates with deep Java, Go, or other enterprise backend experience will be considered if they have led complex legacy replacement and migration work
• Significant hands-on data migration experience, including profiling, transformation, reconciliation, exception handling, and parallel-run validation before cutover
• Strong integration architecture skills, including API and feed contracts, idempotency, retry and error handling, observability, and reconciliation across systems
• Production experience with Kubernetes and CI/CD pipelines in controlled enterprise environments
• Experience delivering in regulated or security-conscious environments with strict controls around access, auditability, sensitive data, secrets, and change management
• Comfortable in a client-facing role, leading discussions with technical teams and business SMEs
• Excellent written and verbal communication skills in English
• Ability to work independently in a remote, fast-paced environment
• Candidates must be willing to comply with healthcare data privacy and security agreements
• Будет плюсом: experience with royalty, residual, or rights-based payment systems, experience with pension or benefit plans, multiemployer plans, or union-related systems, experience in HIPAA-regulated environments, familiarity with Azure DevOps, on-premises Kubernetes, or modern web front-end frameworks such as Next.js

• The engagement begins with a discovery phase, followed by a multi-month build through production cutover
• Strong overlap with US Pacific Time