All my executions disappeared after reaching 100k; how to fix and prevent again?

I believe, yes, that is the default.

And that is odd, tho. I am not confident if that means total or per workflow, to be frank.

There may be a chance to recover, but more likely not, what is the database type you are using for n8n?

Have you recently restarted the docker container? It could have been a glitch it didn’t delete if not explicitly setup. And a restart could have “reset” that.