Drupal 8 Backup-Migrate running into out-of-memory Error? A large key_value_expire table may be the cause!

On a customer page we were running into problems with backup_migrate aborting with out of memory errors. In contrast to other similar websites we found out that a bug ([#2931611]) in the honeypot module caused the key_value_expire database table to grow up to 2,3 GB of (useless) data.
This bug in detail is being targeted in this issue: [#2997609]

So if you're running into such kind of problems, evaluate the size of your database tables and if the results make sense to you.

If everything is fine there, you'd like to help with this issue: [#3045137] for Drupal 8.