MySQL and HBase integration?

I plan to create a social network with a feed like tweeter's, I planed to use MySQL at first but knew I would need something more 'specialized' for big systems. I decided it would be HBase because of it's BigTable schema that best suits the tweeter-style feed I want.

I want to know if there is a simplier or better solution than the one I came up with, please write your suggestions and the problems you might see in my approach.

The Solution I came up with:

I would have all the user's static information(data that doesn't change as often as a post for example) and the User relation with other entities(Groups & followers) in MySQL. The Feedback service in HBase.

For example my system has a many-to-many relationship from 'users' to 'groups' table (One user might be subscribed to many groups and one group might have many subscribers); when new content is posted on a group I could rapidly retreive a list of users following that group from the intermediate table in the relationship and in HBase make the actual data insert in the feed with the corresponding user-key in a 'fan-out on write' manner. This way MySQL can handle what is best for(relationships), and HBase will only make the data delivery(and what it implies: comments, likes, etc.) based on a key list.

This way if a relationship changes or it's deleted(User stops following someone) HBase doesn't receive the key and no information is written on that user's feed. If a user subscribes to a group a new relation is created, and consequently a key will be added to the list next time it's passed to HBase.