A coworker of mine just asked me if we should make the connection string read only to the web database, on the CD server. I have never seen it done before when hardening the CD servers, but its an interesting question. My first thought it that you couldn't because of the CD server being able to update the Event Queue information. But has anyone ever tried to harden the connection string for the web database on the CD server?
No, you don't want to make the connection string Read Only.
The reason behind his is that the EventQueue table is actually written to by the CD server when doing tasks. There are a number of processes that occur on the CD server that perform writes to the web database.
Yeah, we've tried to harden it to readonly in the past (not for version 8, but for an earlier version of Sitecore) and it worked, but we started noticing that content wouldn't get updated appropriately, and then the eventqueue/history table would grow really large and not be maintained appropriately.
I wouldn't suggest it.