I run a middle size community and some time ago I started to develop social capabilities such as follow, status update, wall etc.

For some reason i thought that Cassandra was the right tool for the job so I looked online for a Cassandra developer and I found a very talented one.

Unluckily in the midst of the development the dev left (too much jobs) and so I'm here with a very nice class, a very nice demo, but a lot of fears that I won't be able to handle basic things such as compaction, scaling etc.

My biggest fear is to go online with all this coolness and then having a site inaccessible for hours or days.

The mysql consultant (very talented too) keeps saying me that I should stick with Mysql which I know rather well and in case something's wrong we can manage.

In that case I should take the class made for cassandra and abstract it for Mysql.

My question is this: Should I find another dev/consultant and stick with Cassandra because for social things it is definitely the best tool for the job, or should I listen to the Mysql consultant and revert to Mysql?

About 15k login each day Average 20 actions per user Avg 6 followers x user

(These are current statistics, but of course I'd like to increase them as much as possible.)