Java Engineer – Application / Database Modernization (Freelancer)

Mactores is the agent-native AWS modernization firm. Most modernization work doesn't ship, it stalls in pilots, slips a year, or lands at three times the budget. We exist to ship it: production systems running, legacy retired, outcomes measured. Our delivery is built on Aedeon, the agent platform built by Mactores' founders' sister company, which absorbs the repetitive 60–70% of engagement work, discovery, dependency mapping, validation, test generation, that traditional consulting bills human hours against. Forward-deployed engineers own the rest: architecture, judgment, and cutover, on dates we commit to in the contract.

What you will do?

Analyze and remediate large enterprise Java codebases to replace legacy or database-specific SQL constructs with modern, standards-compliant SQL.

Convert embedded SQL within Java services and MyBatis XML mappers, including rewriting constructs such as vendor-specific functions, sequences, pagination logic, dynamic SQL, and error-handling patterns.

Collaborate closely with schema and database migration engineers to ensure application-layer SQL aligns with the modernized target schema.

Refactor Java transaction logic, error-handling, drivers, and ORM/DAO layers to support the behavior of modern databases.

Participate in unit, integration, and performance testing to confirm functional parity and ensure applications meet performance SLAs post-modernization.

Support application cutover activities for production environments, including validation, monitoring setup, rollback planning, and stabilization.

Produce engineering documentation: SQL remediation guides, code-migration runbooks, troubleshooting guides, and knowledge-transfer material for customer teams.

Work across distributed teams (US & India) and collaborate with customer SMEs to ensure business logic alignment and successful modernization outcomes.

What are we looking for?

Bachelor’s degree in Computer Science, Engineering, or related field.

3+ years of professional Java development experience (Spring, JDBC, MyBatis/Hibernate or equivalent).

Experience with application modernization, database migrations, or large-scale refactoring initiatives.

Strong SQL expertise and the ability to analyze, interpret, optimize, and rewrite complex SQL used within Java applications.

Deep understanding of JDBC, ORMs, Java transaction patterns, and database-driven application flows.

Experience working on enterprise-grade, high-performance applications with complex data interactions.

Strong communication skills and ability to work with global distributed teams in US time-zones.

You will be preferred if

Experience with PostgreSQL, Aurora PostgreSQL, or modernization 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 modernization projects.