SlackBuildsOrg/system/profile-sync-daemon

Profile-sync-daemon (psd) is a tiny pseudo-daemon designed to manage
your browser's profile in tmpfs and to periodically sync it back to
your physical disc (HDD/SSD). This is accomplished via a symlinking
step and an innovative use of rsync to maintain back-up and
synchronization between the two. One of the major design goals of
psd is a completely transparent user experience.

Note:
I strongly encourage reading the ArchWiki article
https://wiki.archlinux.org/index.php/Profile-sync-daemon
before starting, and stopping the daemon in /etc/rc.d/rc.local_shutdown.