Software Engineer for Legacy Codebase Migration

Apply deep production migration expertise to help a frontier AI research lab evaluate and improve complex software modernisation work modelled on real-world, enterprise-scale legacy systems. Role Overview

This role is for experienced software engineers who have personally delivered complex migrations in large production environments, especially within financial services, fintech and payments, insurance, healthcare, telecommunications, large technology companies, or other mission-critical enterprises. Ongoing work may be available as the research program expands.

• 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.
• Maintain functionality, backward compatibility, data integrity, security, and performance throughout migrations.
• Create testing and validation strategies that identify regressions and behavioural differences.
• Assess AI-generated migration solutions for correctness, completeness, maintainability, and production readiness.

• 5+ years of professional software engineering experience, ideally at Senior, Staff, Principal, or equivalent level.
• Deep hands-on experience with legacy codebase migration and modernisation, including personal ownership of or substantial technical contributions to large-scale production migrations.
• Experience working with mature systems that involve 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 analyse unfamiliar codebases and diagnose subtle migration failures.
• Experience with one or more migration areas, including Java 8 to 17/21, legacy .NET to modern .NET, Python 2 to 3, PHP 7 to 8, COBOL to Java or Python, or JavaScript to TypeScript.
• Experience modernising frameworks such as Angular, Rails, Django, Spring or Spring Boot, ASP.NET, Next.js, Astro, or comparable frameworks.
• Experience migrating databases and ORMs, such as Oracle or MySQL to PostgreSQL, SQL to NoSQL, Hibernate to jOOQ, Sequelize to Prisma, or raw SQL to an ORM.
• Experience with infrastructure modernisation, including VMs or bare metal to containers, Docker, Kubernetes, or cloud-native architectures.
• Experience updating CI/CD systems, build and package tooling, APIs, authentication, repository structures, testing frameworks, or deprecated dependencies, runtimes, APIs, and vendor SDKs.
• Especially valuable experience includes modernising core banking, payments, trading, insurance, healthcare, telecommunications, or other high-reliability systems.
• 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.

• Remote hourly engagement.
• Work focuses on technically challenging software modernisation problems based on production-scale legacy systems.
• An open-source maintainer background is not required.

$200 per hour.