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Java Jobs in Downey, CA

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Last updated: 11 days ago

Remote Legacy Codebase Migration Expert - AI Trainer ($200-$200 per hour)

MercorCerritos, California, US
RemoteRemote
Part-timePart-time

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... Show more

Java Architect

TradeJobsWorkForce90044 Los Angeles, CA, US

Java Architect Job Duties: Achieves e-commerce information architecture operational objectives by contributing information and recommendations to strategic plans and reviews; preparing and completi... Show more

 • Promoted

Remote Legacy Codebase Migration Expert - AI Trainer ($200-$200 per hour)

MercorBuena Park, California, US
RemoteRemote
Part-timePart-time

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... Show more

Remote Legacy Codebase Migration Expert - AI Trainer ($200-$200 per hour)

MercorLynwood, California, US
RemoteRemote
Part-timePart-time

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... Show more

Senior Data Scientist

CIM GroupLos Angeles, California, United States, 90001

CIM is a community-focused real estate and infrastructure owner, operator, lender, and developer.Our team of experts works together to identify and create value in real assets, benefiting the commu... Show more

Remote Legacy Codebase Migration Expert - AI Trainer ($200-$200 per hour)

MercorLakewood, California, US
RemoteRemote
Part-timePart-time

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... Show more

Remote Legacy Codebase Migration Expert - AI Trainer ($200-$200 per hour)

MercorMonterey Park, California, US
RemoteRemote
Part-timePart-time

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... Show more

Remote Legacy Codebase Migration Expert - AI Trainer ($200-$200 per hour)

MercorLa Mirada, California, US
RemoteRemote
Part-timePart-time

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... Show more

Remote Legacy Codebase Migration Expert - AI Trainer ($200-$200 per hour)

MercorMontebello, California, US
RemoteRemote
Part-timePart-time

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... Show more

Senior Fullstack Developer

Newhouse Project ConsultingNorwalk, California, United States

We have an opportunity for an experienced Senior Software Engineer to lead the development, enhancement, and support of multiple business applications.This role combines hands-on software engineeri... Show more

Remote Legacy Codebase Migration Expert - AI Trainer ($200-$200 per hour)

MercorBell Gardens, California, US
RemoteRemote
Part-timePart-time

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... Show more

Remote Legacy Codebase Migration Expert - AI Trainer ($200-$200 per hour)

MercorNorwalk, California, US
RemoteRemote
Part-timePart-time

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... Show more

Remote Legacy Codebase Migration Expert - AI Trainer ($200-$200 per hour)

MercorWhittier, California, US
RemoteRemote
Part-timePart-time

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... Show more

Remote Legacy Codebase Migration Expert - AI Trainer ($200-$200 per hour)

MercorDowney, California, US
RemoteRemote
Part-timePart-time

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... Show more

Remote Legacy Codebase Migration Expert - AI Trainer ($200-$200 per hour)

MercorBellflower, California, US
RemoteRemote
Part-timePart-time

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... Show more

Remote Legacy Codebase Migration Expert - AI Trainer ($200-$200 per hour)

MercorHuntington Park, California, US
RemoteRemote
Part-timePart-time

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... Show more

Remote Legacy Codebase Migration Expert - AI Trainer ($200-$200 per hour)

MercorCompton, California, US
RemoteRemote
Part-timePart-time

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... Show more

Remote Legacy Codebase Migration Expert - AI Trainer ($200-$200 per hour)

MercorSouth Gate, California, US
RemoteRemote
Part-timePart-time

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... Show more

Remote Legacy Codebase Migration Expert - AI Trainer ($200-$200 per hour)

MercorParamount, California, US
RemoteRemote
Part-timePart-time

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... Show more

Remote Legacy Codebase Migration Expert - AI Trainer ($200-$200 per hour)

MercorPico Rivera, California, US
RemoteRemote
Part-timePart-time

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... Show more

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Remote Legacy Codebase Migration Expert - AI Trainer ($200-$200 per hour)

Remote Legacy Codebase Migration Expert - AI Trainer ($200-$200 per hour)

MercorCerritos, California, US
30+ days ago
Job type
  • Part-time
  • Remote
Job description

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, , 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.