spotify_sync is a CLI application that downloads Spotify-liked songs and playlists by matching them to Deezer equivalents via ISRC and downloading the matched tracks. It features a modular architecture with separate components for Spotify API interaction, Deezer matching/downloading, persistent data storage, and configuration management. Key features include multi-threaded downloading, scheduling, Pushover notifications, and Plex library scanning via Autoscan. The application supports multiple profiles for different Spotify accounts and includes robust configuration validation with legacy migration capabilities.