The Refresh Key acts as a special credential used specifically to obtain a new Access Token without requiring the user to re-enter their credentials.

: For IoT devices with limited battery life, developers use "Lightweight Key Freshness Schemes" (like XKFS) to refresh security keys without using too much energy. Summary Table: Refresh Keys by Context Chromebook Not Waking Up from Sleep Mode - Acer Community

Unlike Access Tokens, Refresh Keys are "stateful." This means the server usually keeps a record of them in a database (often using Redis for speed).