Subaru

⚪Unreviewed

Posted

2026-10-31T17:16:51.000000Z

Java / Spring Boot — API bug fixing & REST API development

500s, hanging endpoints, slow queries, broken auth? I read the logs, trace the flow and fix the root cause — not a try/catch on the symptom.

Production ERP background, where downtime costs money by the minute. Diagnosis through logs and data, fix, and a commit that explains what was actually wrong.

Fixing & maintenance:
- 500s, NullPointer, unhandled exceptions
- Endpoints returning bogus 401/403
- JWT and Spring Security misconfiguration, broken role checks
- N+1 queries, missing indexes, slow endpoints
- Data inconsistency repair and recovery via SQL (PostgreSQL, Firebird)

Building:
- REST APIs with Spring Security, JWT and RBAC
- PostgreSQL with JPA/Hibernate, versioned Flyway migrations, DTO layer
- Third-party API integration, Resilience4j rate limiting
- Vue 3 + TypeScript frontend wired to your API
- Docker environment, JUnit/Mockito tests

How I work:
- Written scope and deadline before a single line of code — in and out of scope, in writing
- Fixes: 50% on quote approval, 50% on delivery. Builds: 40% on approval, 40% at first working deploy, 20% on delivery
- Everything over text, async-friendly. Written English only, so nothing gets lost in a call.
- Repo with clean commits and README, reply within 3h

Overlaps full US business hours (UTC-3, until 6pm local).

Projects: multi-tenant financial API (34 endpoints, RBAC 5 roles, JWT HttpOnly cookies, Flyway, soft delete).

Java 17, Spring Boot, Spring Security, JPA/Hibernate, PostgreSQL, Firebird, Flyway, Resilience4j, Vue 3, TypeScript, Docker, Git.
github.com/MatheusCristophi · linkedin.com/in/matheuscristophi · DM or matheuscr909@gmail.com

Diagnosis $30–40/h (1h min, root cause and fixed quote before any change). APIs from $350, quoted per scope. Send the endpoint list or the stack trace and I'll come back with quote and deadline.