The database under a hosted Drupal or Backdrop estate has to change generations one day, and that is the day most operators find out what their migration tooling was hiding. On a BOA box the move across Percona generations is a rehearsed road: a readiness check names the one account which would block the whole box, the single-account mover carries an account to the newer server with passwords, PHP versions and search indexes intact and the old box relaying traffic until DNS moves, and the whole-server mover refuses to cross a version at all, on purpose, because it replicates rather than dumps. Every transfer and every cutover is a dry run first, every dry run is spent on use, and the watchdog which rescues stuck databases stands down for exactly the minutes it would otherwise rescue you from your own migration.