Awhile back I had to move a MariaDB database that should have been tiny. When we actually went to look at it, it was over 400GB and obviously the first question was WTF. The developers had decided to log to a table which did make for really simple ways to query the logs, but caused us to have to get a bit creative in the migration (which was actually kind of fun in the end). I'm sure it's been done many times, but it's the first time I had run into it.