But above all, it's a solution to two real problems I had.
I work in several terminals. Sometimes tabs or Windows in my emulator, sometimes screen or tmux. And all those sessions would overwrite eachothers history. I lost many actual important history entries that way. And I (almost) ran many wrong commands, expecting another one to be my last entry. Arrow-up enter. Woops.
Atuin solved this.
I had my history as large as possible. Ctrl-r is my friend to search for "that old thing I did to pgsql piping something from zcat a year ago". But it's ever slower, zsh and bash history clearly not designed to handle (tens of) thousands of entries.
Atuin solved this.