Java Engineer, Application and Database Modernization

Mactores is an AWS modernisation consultancy that runs engagements with an agent platform absorbing the mechanical work while its engineers own the judgement. This role sits on a specific mission: an Oracle to PostgreSQL migration where the platform handles bulk conversion at scale and you own the refactoring judgement inside large enterprise Java codebases. Concretely you would rewrite the SQL the application actually depends on, convert embedded SQL in Java services and MyBatis XML mappers including vendor specific functions, sequences, pagination and dynamic SQL, and refactor Java transaction logic, error handling, drivers and ORM or DAO layers to match modern database behaviour. Then you prove functional parity through unit, integration and performance testing, and see the application through production cutover with rollback planning and stabilisation. The posting is blunt about the point of it: not a proof of concept, a system that ships.

What the posting requires:
- A Bachelor's degree in Computer Science, Engineering or a related field.
- 5+ years of professional Java development experience with Spring, JDBC, and MyBatis or Hibernate or equivalent.
- Experience with application modernisation, database migrations or large scale refactoring initiatives.
- Strong SQL expertise: you can analyse, interpret, optimise and rewrite complex SQL embedded in Java applications.
- Deep understanding of JDBC, ORMs, Java transaction patterns and database driven application flows.
- Experience on enterprise grade, high performance applications with complex data interactions.
- Strong communication skills and the ability to work with globally distributed teams in US time zones.

Nice to have:
- Experience with PostgreSQL or Aurora PostgreSQL, or modernisation from legacy databases such as Oracle, SQL Server or DB2.
- Exposure to automated code refactoring tools or GenAI assisted remediation workflows.
- Familiarity with CI/CD environments, performance testing tools and observability stacks.
- Consulting or professional services experience delivering fixed timeline modernisation projects.

What the work actually looks like:
- Analyse and remediate large enterprise Java codebases, replacing legacy and database specific SQL constructs with modern, standards compliant SQL.
- Convert embedded SQL in Java services and MyBatis XML mappers: vendor specific functions, sequences, pagination logic, dynamic SQL and error handling patterns.
- Work with schema and database migration engineers so application layer SQL lands aligned with the modernised target schema.
- Refactor Java transaction logic, error handling, drivers and ORM or DAO layers.
- Run unit, integration and performance testing to confirm functional parity and hit performance SLAs after modernisation.
- Support production cutover: validation, monitoring setup, rollback planning and stabilisation until the system holds.
- Produce engineering documentation that outlives the engagement: SQL remediation guides, code migration runbooks, troubleshooting guides and knowledge transfer material.

What the company says about how the work splits: the agent platform does the repetitive 60 to 70 percent that a traditional consulting engagement would staff humans for, including mechanical SQL conversion and the regression harness. Your hours go to the refactoring judgement.

Location and working pattern: Mumbai, with distributed collaboration across US and India teams and an expectation of overlap with US time zones.

Honest fit guidance: this is deep, unglamorous, high value work. If you have lived inside a large Java codebase with vendor specific SQL, five years is enough. If your Java is greenfield microservices only, the legacy remediation requirement is the gap.