Are there any pitfalls with having multiple MySQL databases on 1 server node?

[John Smith]

I want to prepare my database for sharding in the future. But right now I only need 1 node.

What I'd like to do is to shard the database into virtual shards, say 12 shards, and put all of them onto the same server node for now.

And when I need to scale out, I could just then get a 2nd server and move 6 of the 12 virtual shard onto the new machines.

Are there any pitfalls with having 12 different databases on 1 machine?

* Can I still run only 1 MySQL instance to support those 12 databases?
* Does having 12 databases result in higher memory usage? How much higher?
* Does this require having 12X as many database connections?
* Any other pitfalls?

Thanks.