Legacy Codebase Migration Expert (remote)
About the role
Mercor is partnering with a frontier AI research lab to engage experienced software engineers with deep expertise in legacy codebase migration and modernisation. We are looking for engineers who have personally executed complex migrations across large, production-grade systems, particularly in financial services, fintech/payments, insurance, healthcare, telecom, large technology companies, and other mission-critical enterprises. Strong hands-on experience with production migrations is the primary qualification. What You'll Do - Design, implement, review, and evaluate complex codebase migration and modernisation tasks. - Analyse legacy code, dependencies, APIs, databases, build systems, and infrastructure to determine safe migration approaches. - Preserve functionality, backwards compatibility, data integrity, security, and performance during migrations. - Develop tests and validation strategies to identify migration regressions and behavioural differences. - Evaluate AI-generated migration solutions for correctness, completeness, maintainability, and production readiness. Relevant Migration Experience Candidates should have deep expertise in one or more of the following: - Language/version: Java 8 → 17/21, legacy .NET → modern .NET, Python 2 → 3, PHP 7 → 8 - Language rewrites: COBOL → Java/Python, JavaScript → TypeScript - Frameworks: Angular, Rails, Django, Spring/Spring Boot, ASP.NET, Next.js/Astro, and other major framework upgrades/replacements - Databases & ORMs: Oracle/MySQL → PostgreSQL, SQL → NoSQL, Hibernate → jOOQ, Sequelize → Prisma, raw SQL → ORM - Infrastructure: VMs/bare metal → containers, Docker/Kubernetes, cloud-native architectures - CI/CD: Jenkins/Travis → GitHub Actions, GitLab CI, or modern deployment pipelines - Build/package tooling: Maven → Gradle, Webpack → Vite, CRA → Next.js, npm → pnpm - APIs: REST → GraphQL, HTTP/REST → gRPC, SOAP/legacy APIs → modern interfaces - Authentication: Legacy auth → OAuth/OIDC, SAML/SSO, modern identity and authorisation systems - Repositories: Polyrepo → monorepo using Bazel, Nx, Turborepo, or similar - Testing: Migration of unit, integration, browser, and E2E testing frameworks - Dependencies/SDKs: Replacement of deprecated or EOL libraries, APIs, runtimes, and vendor SDKs Ideal Background - 5+ years of professional software engineering experience, ideally Senior, Staff, Principal, or equivalent. - ... Pay: $200 an hour (USD). Remote contract work through Mercor. Apply on Mercor, upload your CV and complete a short AI interview.