Software Engineer Legacy Codebase Migration

Help advance frontier AI research by applying hands-on expertise in modernising large, production-grade legacy software systems. This role focuses on complex migrations in mission-critical environments, including financial services, fintech and payments, insurance, healthcare, telecommunications, large technology companies, and similar enterprises.

• Design, implement, review, and evaluate complex codebase migration and modernisation work.
• Analyse legacy code, dependencies, APIs, databases, build systems, and infrastructure to determine safe migration approaches.
• Maintain functionality, backward compatibility, data integrity, security, and performance throughout migrations.
• Create tests and validation approaches that identify regressions and behavioural differences.
• Assess AI-generated migration solutions for correctness, completeness, maintainability, and production readiness.

• At least 5 years of professional software engineering experience, ideally at Senior, Staff, Principal, or equivalent level.
• Deep expertise in legacy codebase migration and modernisation, with personal ownership of or substantial contributions to large-scale production migrations.
• Experience working with mature systems that have 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 quickly understand unfamiliar codebases and diagnose subtle migration failures.
• Experience modernising core banking, payments, trading, insurance, healthcare, telecom, or other high-reliability systems is especially valuable.
• For COBOL or mainframe modernisation, experience with z/OS, CICS, JCL, DB2, VSAM, batch processing, and COBOL-to-Java or Python migrations is particularly valuable.

Deep expertise in one or more of the following migration areas is required:

• Language and version upgrades, including Java 8 to 17 or 21, legacy .NET to modern .NET, Python 2 to 3, and PHP 7 to 8.
• Language rewrites, such as COBOL to Java or Python, and JavaScript to Type Script.
• Framework upgrades or replacements involving Angular, Rails, Django, Spring or Spring Boot, ASP.NET, Next.js, Astro, or similar frameworks.
• Database and ORM migrations, including Oracle or MySQL to PostgreSQL, SQL to No
  
  SQL, Hibernate to jOOQ, Sequelize to Prisma, and raw SQL to an ORM.
• Infrastructure modernisation from VMs or bare metal to containers, Docker, Kubernetes, or cloud-native architectures.
• CI/CD migrations from Jenkins or Travis to Git Hub Actions, Git Lab CI, or modern deployment pipelines.
• Build and package tooling migrations, including Maven to Gradle, Webpack to Vite, CRA to Next.js, and npm to pnpm.
• API modernisation, including REST to GraphQL, or REST to gRPC, and SOAP or legacy APIs to modern interfaces.
• Authentication migrations from legacy systems to OAuth/OIDC, SAML/SSO, or modern identity and authorisation systems.
• Repository consolidation from polyrepo to monorepo using Bazel, Nx, Turborepo, or similar tooling.
• Migration of unit, integration, browser, and end-to-end testing frameworks.
• Replacement of deprecated or end-of-life libraries, APIs, runtimes, and vendor SDKs.

Remote, hourly engagement.

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

Open-source maintainer experience is not required.

Ongoing work may be available as the research program expands.

$200 per hour.