How many databases can an Amazon Aurora instance hold?
I'm speaking to the currently available version of Aurora which is MySQL 5.6 compatible. On the surface, it works just like MySQL. I have two databases on my Aurora cluster. My guess it can hold as many databases as MySQL or at least more than you would ever need. Where things differ is in how backups are handled. Aurora, like other RDS offerings, does cluster snapshots, not individual database backups. To restore a cluster snapshot, you actually create a new Aurora cluster, switch DNS to the new cluster, and then delete the source cluster. This means that if you have problems with one of your databases on a cluster, you have to restore all databases at the same time. So you might want to group application databases together. For instance, all our ticketing and code review software (Jira and Fisheye) run on the same Aurora cluster. The two apps are used hand-in-hand so the two would always need to be restored together.