I will fix and develop java spring boot, python rest API backend

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Y
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Yuna Lee
fix and develop java spring boot, python rest API backend
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fix and develop java spring boot, python rest API backend

About this gig

Is your Java or Python backend broken, slow, or incomplete?

I can help.

With 7+ years of backend experience in financial IT and B2B/B2C production systems, I deliver clean, reliable, and production-ready code not just quick patches.

I specialize in:

  • Fixing bugs and errors in Spring Boot / Python applications
  • Building REST API endpoints (Java Spring Boot, Python FastAPI/Flask)
  • Optimizing slow database queries (PostgreSQL, MySQL, Oracle)
  • Microservices & MSA architecture
  • Docker deployment & cloud basics (AWS, NCP)
  • Code review and refactoring

Real results from production systems:

  • Fixed service crashes caused by multi I/O structure
  • Query response time improved 10x (2s 0.2s)
  • Eliminated 400+ monthly data inconsistencies
  • Cut process time 50%+ via backend restructuring

What I work with:

  • Java 8 / 11 / 17 / 21
  • Python
  • Spring Boot, Spring MVC, Spring Batch
  • REST API, RESTful design
  • PostgreSQL, MySQL, Oracle
  • Microservices, MSA architecture
  • Docker, AWS basics

How it works:

  1. Share your code or describe the issue
  2. I review and confirm scope before starting
  3. I fix/build and deliver with clear documentation
  4. Revision included if needed

Not sure which package fits? Message me first I'll re

  • Programming language

    • Java

  • Expertise

    • Algorithms & Data structures
    • Debugging
    • Performance
    • Databases
    • Source control

  • Frontend framework

    • jQuery

  • Backend framework

    • Spring

Get to know Yuna Lee

Yuna Lee

Experienced Backend Software Engineer with Proven Multi Project Portfolio

  • FromSouth Korea
  • Member sinceMar 2026
  • Avg. response time1 hour

  • Languages

    English, Korean
Java Backend Engineer | Spring Boot · MSA · REST API 7+ years in Financial IT & B2B/B2C platforms. What I've delivered: • Cut process time 50%+ → sales 30% to 70% • Eliminated 400+ monthly data inconsistencies → 0 • Query response 10x faster (2s → 0.2s) • Resolved service crashes via refactoring I find root causes, not quick patches. Full cycle: Requirements → Design → Dev → QA → Stabilization. Also led an AI-based insurance recommendation PoC. Available for Java backend, API development, bug fixes, and performance optimization. Feel free to message me before ordering.

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