Freelance Full-Stack Developer

We have a working internal web application — a single-page React/Node.js tool used internally for calculating and sizing batteries for UPS (Uninterruptible Power Supply) systems. The app currently runs on our internal network only. We're looking for an experienced freelance developer to enhance, harden, and prepare this application for secure public deployment. Ideal Candidate - Strong hands-on experience with React and Node.js - Demonstrated experience implementing or hardening role-based access control - Comfortable working through formal internal security review/sign-off processes, not just a one-time audit - Based in or able to work substantially overlapping hours with CET (Central European Time) preferred, not required Engagement Details - Duration: Estimated 4–8 weeks depending on scope finalization - Structure: Fixed price per phase, paid as milestones