Legacy Codebase Migration Expert

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, → 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.

• Personally owned or made substantial technical contributions to large-scale production migrations .

• Experience working with mature systems involving technical debt, complex dependencies, legacy integrations, and significant regression risk.

• Strong knowledge of compatibility, testing, observability, staged rollouts, rollback strategies, and behavioural equivalence .

• Ability to reason deeply about unfamiliar codebases and diagnose subtle migration failures.

• Especially valuable: engineers who have modernised core banking, payments, trading, insurance, healthcare, telecom, or other high-reliability systems .

• For COBOL/mainframe modernisation, experience with technologies such as z/OS, CICS, JCL, DB2, VSAM, batch processing, and COBOL-to-Java/Python migrations is particularly valuable.

Why Join

• Apply your migration expertise to help shape how frontier AI models understand and execute complex software modernisation .

• Work on technically challenging problems modelled after real-world, production-scale legacy systems .

• Contribute expertise developed from large enterprise migrations without needing an open-source maintainer background.

• Opportunity for ongoing work as the research program expands.