Optimize TikTok Downloader Performance and Features

I’ve built an online TikTok downloader that works, but it still feels rough around the edges. I’d like to take it to the next level by making downloads noticeably faster, polishing the mobile experience, and adding the option to grab audio-only files. Here’s what I need help with: • Speed boost – Diagnose current bottlenecks (API calls, server latency, file streaming, throttling, etc.). – Refactor or re-architect so a typical video downloads significantly quicker for end users. – Keep bandwidth usage and server costs reasonable while improving throughput. • Mobile-first interface – Redesign key pages for small screens (responsive layout, thumb-friendly buttons, clear progress indicators). – Ensure smooth performance on both Android and iOS browsers. • Audio file support – Add a “Download Audio” option that extracts and delivers high-quality MP3 or AAC from the same TikTok link. – Maintain original metadata (title, creator handle) when possible. Please work within my existing tech stack (HTML/CSS/JavaScript on the front end, Node.js on the back end with FFmpeg in the pipeline). Clean, well-commented code and a short deployment guide are required so I can maintain everything myself later. If you’ve optimized media downloaders before or have strong experience with FFmpeg, CDN integration, or caching for large files, I’d love to see examples.