You will get backend bugs fixed fast with clean, tested code
Project details
You will get your backend bug fixed properly — not a quick patch that breaks something else, but a real fix with tests and a clear explanation of what went wrong.
I have debugged payment systems at Santander Bank and untangled legacy codebases in telecom. I work with Java/Spring Boot primarily but also fix issues in Node.js, Python, and Supabase backends.
Every fix includes: the solution, a test that proves it works, and a written root cause explanation. If I spot other problems while fixing yours, I flag them for free.
I have debugged payment systems at Santander Bank and untangled legacy codebases in telecom. I work with Java/Spring Boot primarily but also fix issues in Node.js, Python, and Supabase backends.
Every fix includes: the solution, a test that proves it works, and a written root cause explanation. If I spot other problems while fixing yours, I flag them for free.
Programming Languages
Python, Java, TypeScriptCoding Expertise
Performance Optimization, SecurityWhat's included
| Service Tiers |
Starter
$80
|
Standard
$250
|
Advanced
$500
|
|---|---|---|---|
| Delivery Time | 2 days | 5 days | 7 days |
Number of Revisions | 1 | 2 | 2 |
Bug Investigation | |||
Fix Documentation | - | ||
Detailed Code Comments | - | - |
Optional add-ons
You can add these on the next page.
Fast Delivery
+$30 - $100
Additional Revision
+$20
Fix Documentation
(+ 1 Day)
+$30
Detailed Code Comments
+$50
Automated test coverage
(+ 2 Days)
+$80
Performance profiling
(+ 3 Days)
+$120
Post-fix monitoring 7 days
+$50Frequently asked questions
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SM
Sampath Kumar M.
Mar 28, 2023
Small programming fix in Java or Groovy
Volodymyr was able to quickly identify the problem and was able to solve the issue without much difficulty.
The code was decent and was able to solve my problem easily. I strongly recommend Volodymyr for any similar jobs.
The code was decent and was able to solve my problem easily. I strongly recommend Volodymyr for any similar jobs.
About Volodymyr
Payment & API Backend Engineer | Java, Spring Boot, Ex-Banking
Alicante, Spain - 5:59 pm local time
I help startups and SaaS teams build reliable web apps, backend systems, APIs, payment flows, and frontends - and audit existing products before they scale. I'm a Java / Full-Stack Engineer with 4 years of experience across banking, telecom, IoT, and SaaS, including payment systems at Santander Bank. My core is backend engineering, and I ship complete products end to end - from database schema and APIs to a production-ready React / Next.js frontend.
WHERE I CAN HELP
→ MVP from scratch: backend, database, APIs, authentication, admin panels, integrations, deployment, and frontend.
→ Stabilizing an existing MVP: cleaning up unstable code, fixing broken flows, improving architecture, adding tests, and preparing the product for real users.
→ Technical audit and code analysis: architecture review, code audit, performance and reliability analysis, scalability and security risks - delivered as a prioritized report with quick wins and a clear fix plan. Useful before scaling, investment due diligence, or taking over a codebase from another team.
→ Payments and revenue-critical systems: Stripe API, transaction flows, retries, idempotency, and failure-safe backend logic.
→ Frontend development: React / Next.js applications, TypeScript, Tailwind, client-facing product flows, admin interfaces, and tight integration with backend APIs.
→ SaaS and internal platforms: dashboards, admin tools, workflow automation, provisioning systems, and developer tooling.
→ Backend architecture and scaling: Spring Boot, PostgreSQL, Kafka, Docker, Kubernetes, AWS, CI/CD, testing, and production support.
RESULTS I'VE SHIPPED
→ Santander Bank: built instant payment features that cut transaction processing time by 12%. Coordinated 8 cross-functional teams across 4 releases on systems where reliability directly affected financial operations.
→ Friendly Technologies: led backend development for TR-069 / TR-369 IoT device-management products — services, APIs, provisioning, QA environments, internal developer platforms, Kubernetes tooling, and AI-assisted engineering workflows.
→ Simbio (pet-sitters platform): built and improved backend APIs handling 500+ daily bookings, implemented real-time WebSocket chat, and reduced server response times by 35%.
→ Workflow automation: integrated Flowable BPMN into enterprise systems, cutting manual process steps by ~40%.
HOW I WORK
I ask the right questions upfront, flag product risks early, break work into clear milestones, and deliver clean, maintainable code with tests. You won't need to chase me for updates — I communicate progress clearly and focus on shipping a working product, not just writing code.
STACK
Backend: Java 8–25 · Spring Boot · PostgreSQL · MySQL · Oracle · Kafka · RabbitMQ · Redis · Hazelcast · REST / SOAP APIs · Stripe API
Frontend: React · Next.js · TypeScript · Tailwind · Vite
Infra & QA: Docker · Kubernetes · AWS · GitHub Actions · Jenkins · Testcontainers · JUnit
Send me a short description of your product, MVP, or existing codebase - I'll reply with a specific technical approach, the main risks I see, and the first steps I would take.
Steps for completing your project
After purchasing the project, send requirements so Volodymyr can start the project.
Delivery time starts when Volodymyr receives requirements from you.
Volodymyr works on your project following the steps below.
Revisions may occur after the delivery date.
Reproduce the bug
I set up your project locally, reproduce the issue, and confirm I understand the root cause. I message you with my findings before making changes.
Fix and test
I implement the fix, write tests to cover the bug scenario, and verify nothing else broke. You get a PR with clear description of what changed and why.