Both. The library was slow and corrupted data and they were using regular databases along with the event-sourced stuff. That would never work, the whole system

Both. The library was slow and corrupted data and they were using regular databases along with the event-sourced stuff. That would never work, the whole system would have needed to be event sourced for it to have any chance of working. It was essentially a CRUD app with the need for history of changes (for a few tables), SQL was the correct way to do it.