Full Stack Developer Needed for React/Next.js Bug Fixing & REST API Integration

I am looking for a skilled Full Stack Developer to help improve and stabilize our SaaS web application. The ideal candidate should have strong experience with React, Next.js, Node.js, and REST API integrations. This project involves fixing existing bugs, improving application performance, and integrating third-party APIs while maintaining clean, scalable, and secure code. Scope of Work Fix React and Next.js dashboard bugs Resolve login and authentication issues (JWT/OAuth) Debug API data loading and state management issues Integrate third-party REST APIs Build secure backend endpoints using Node.js/Express Implement Stripe and/or PayPal payment gateway integration Improve dashboard features and user experience Optimize page loading speed and overall performance Fix responsive UI issues across devices Resolve MongoDB/PostgreSQL database-related issues Add proper error handling, logging, and validation Refactor existing code without breaking functionality Test all implemented features before delivery Tech Stack React Next.js TypeScript Node.js Express.js MongoDB / PostgreSQL REST APIs JWT / OAuth Authentication Stripe / PayPal Tailwind CSS Git Requirements Strong debugging and problem-solving skills Experience with React and Next.js production applications Solid backend development experience with Node.js Experience integrating third-party APIs and payment gateways Ability to write clean, maintainable, and scalable code Excellent communication skills Ability to deliver within 4–6 days Preferred Experience SaaS applications Dashboard development Performance optimization Secure authentication systems Payment processing integrations