Legacy Codebase Migration Expert (Train AI Models Part Time!)

hackajob is collaborating with Mercor to connect them with exceptional professionals for this 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.

- 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.