Technical Lead - Legacy Financial System

We're looking for a hands-on Tech Lead to guide the replacement of a critical financial processing function within a large US benefits organization, separating it from a legacy core system into a standalone application. This is not a typical greenfield build: the legacy source code will not be available, so existing behavior must be reconstructed from database extracts, historical outputs, documentation, and SME workshops, then proven by reconciling the new system against historical results. The ideal candidate has led a legacy replacement or system separation through production cutover and has deep experience with financial transaction systems such as ledgers, fund allocation, reconciliation, and period close. You'll bring strong backend architecture skills (.NET preferred), significant data migration expertise, and production experience with Kubernetes and CI/CD in regulated, security-conscious environments. The engagement begins with a discovery phase, followed by a multi-month build through production cutover.

Key Responsibilities

• Lead an initial discovery phase with the client's product, business, and technology teams to understand the domain, assess the current architecture, and propose the target technical approach.
• Define the team composition and technical roadmap for implementation, then lead the team through build, migration, and cutover.
• Reverse-engineer legacy business rules without access to source code, using database extracts, historical outputs, existing documentation, and SME interviews.
• Design and validate complex financial logic, including contribution processing, weighted allocation across multiple funds, interest recalculation, receivables, period close, and full audit trail.
• Own the migration of full historical data at high volume, including source profiling, transformation, reconciliation, exception handling, and parallel-run validation.
• Design integration architecture with clear 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 resulting technical and business decisions.
• Stay hands-on in design, code, and reviews rather than operating purely as an architect.
• Ensure delivery meets strict requirements around access control, auditability, sensitive data handling, secrets management, deployment controls, and production change management.

Core Requirements

• Proven track record leading a legacy system replacemen t, carve-out, or system separation through production cutover, including personal ownership of the replacement design and involvement through migration. Greenfield-only experience is not sufficient.
• Strong experience with financial transaction systems involving ledgers/subledgers, allocation across funds or accounts, reconciliation, period close, adjustments, and audit trails (pension, insurance, banking, billing, payroll, claims, or similar domains).
• Strong backend architecture experience, with .NET 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 integrationarchitecture 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 both technical teams and business SMEs.
• Excellent written and verbal communication skills in English.
• Ability to work independently in a remote, fast-paced environment.

Nice-to-Have

• Experience with royalty, residual, or rights-based payment systems.
• Experience with pension or benefit plans, multiemployer plans, or union-related systems.
• Experience working in HIPAA-regulated environments.
• Familiarity with Azure DevOps, on-premises Kubernetes, or modern web front-end frameworks such as Next.js.

Additional

• US Timezone Overlap: Strong overlap with US Pacific Time.
• Candidates must be willing to comply with healthcare data privacy and security agreements.
• The client is open on technology choices, so the Tech Lead will be expected to propose the best approach based on discovery findings.
• This role suits someone who enjoys investigative, detail-oriented work: comfortable with ambiguity, methodical about proving legacy behavior through reconciliation, and able to earn trust with business stakeholders.