Browse categories
Explore
Fiverr Pro
English
$
USD
I will fix node js API errors, backend bugs, database, webhooks, authentication issues
Esther B
About this gig
Is your Node.js backend throwing errors, APIs failing, authentication breaking, or your database refusing to connect? I can diagnose and fix the issue without unnecessarily rebuilding your entire application.
I specialize in backend debugging and troubleshooting using Node.js, Express.js, JavaScript, Supabase, Firebase, PostgreSQL, MongoDB, REST APIs, and third-party integrations.
My services include:
- API errors and broken endpoints
- Node.js & Express.js bugs
- Database connection and query errors
- Authentication, JWT & OAuth issues
- Webhook failures
- CORS errors
- Stripe & PayPal integration issues
- REST API integration
- Third-party API errors
- Deployment and server issues
- Backend performance optimization
- Environment and configuration errors
- Firebase & Supabase troubleshooting
- Security and authorization issues
I carefully trace the root cause, implement a clean fix, and test the affected functionality before delivery. Whether you have a small API error or multiple backend issues, I focus on solving the actual problem rather than applying temporary workarounds.
Please contact me before ordering and send the error details, project stack, screenshots/logs, and relevant source code.
Get to know Esther B
Esther B
Backend Developer, API Integration, Node js, Supabase, Firebase, AWS, PostgreSQL
- FromGermany
- Member sinceJul 2026
- Avg. response time8 hours
Languages
German, English, Spanish, French, Italian
Backend developer specializing in scalable APIs, database architecture, and secure web applications. I build REST APIs, backend systems, authentication, payment gateways, AI integrations, and automation workflows using Node.js, Express.js, Supabase, Firebase, PostgreSQL, MongoDB, AWS, and SQL. I integrate Stripe, webhooks, third-party APIs, CRMs, and cloud services while optimizing performance, security, and scalability for SaaS, AI, eCommerce, and custom web applications. I also develop serverless functions, API debugging, cloud deployment, database optimization, and custom backend solutions.
Other Software Development Services I Offer
FAQ
Can you fix my Node.js API errors?
Yes. I diagnose and fix Node.js and Express.js API errors, broken endpoints, server responses, request failures, and integration problems. I trace the root cause instead of applying temporary workarounds, then test the fix to ensure your API works reliably.
Can you fix database connection and query errors?
Yes. I troubleshoot PostgreSQL, MongoDB, Firebase, and Supabase database issues, including failed connections, slow queries, schema problems, and data errors. I identify the underlying cause and optimize the affected database operations for reliable performance.
Can you fix authentication and login issues?
Absolutely. I troubleshoot JWT, OAuth, Firebase Auth, Supabase Auth, sessions, token refresh, permissions, and authorization problems. I ensure your authentication flow works correctly while applying secure backend practices to protect user access and application data.
Can you fix CORS errors?
Yes. I resolve CORS and frontend-to-backend communication problems caused by incorrect origins, headers, credentials, HTTP methods, or server configuration. I configure the backend correctly so your frontend can communicate with your API securely without unnecessary access restrictions.
Can you fix failed webhooks?
Yes. I troubleshoot webhook delivery, authentication, signature verification, endpoint responses, payload handling, and event-processing issues. I can also integrate and test webhooks for Stripe, PayPal, Shopify, and other third-party services to ensure events are processed correctly.
Can you fix Stripe or PayPal integration errors?
Yes. I troubleshoot payment API errors, checkout failures, webhook problems, authentication, payment verification, and subscription issues. I test the complete payment flow and help ensure transactions and backend events are handled correctly and securely.
Can you fix deployment and server errors?
Yes. I troubleshoot backend deployment problems involving environment variables, build failures, server configuration, ports, API URLs, dependencies, and production errors. I can help resolve issues on platforms such as Vercel, Railway, Render, AWS, and similar services.
Can you improve my slow backend or API?
Yes. I identify backend bottlenecks, slow database queries, inefficient API logic, unnecessary requests, and configuration issues. I then optimize the affected areas to improve response times, resource usage, reliability, and overall application performance.
What information do you need to fix my backend?
Please provide the error message, project description, technology stack, relevant logs or screenshots, and source code or repository access when required. Clear information helps me reproduce the problem, identify its cause, and deliver an accurate fix faster.
Should I contact you before placing an order?
Yes. Backend problems vary significantly in complexity. Contact me first with your issue so I can assess the scope, confirm that I can handle it, recommend the appropriate package, and avoid unnecessary costs or incorrect assumptions before work begins.
