About this opportunity
Confidential lists this Software Engineer for Legacy Codebase Migration opportunity in South Gate, California. Review the employer’s description below for duties, qualifications and application requirements.
Job description
Role Overview
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.
Key Responsibilities
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.
Qualifications
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.
Relevant Migration Experience
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 TypeScript.
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 NoSQL, 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 GitHub Actions, GitLab 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, HTTP 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.
Work Terms
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.
Compensation
$200 per hour.
Who can apply
Review the original listing for work authorization, qualifications and employer requirements.