Question about master and read database servers

hi guys

I've got a database server in the cloud that is a master with Amazon. And a read server which replicates from the master.

Now I know that the read server is what will be the 'viewable' server on server pages for security reasons etc for the public to see.

One of the features of this website is that the general public make changes to their profiles and submit/save those changes (i.e. they write to the database). Like you would on a facebook page or a linkedin page when you make changes to your profile.

My question is, can this be possible if the server that is viewable to the public only a 'read' database server? Or does it have to be like a 'master' database for the public to be able to make changes/write to it?

Thank you
Yashy