> Effective search in any real-time messaging platform seems difficult to deliver. Has anyone else had this problem and found a good solution to it?

Log chats to text files and learn `grep`. Keep chat logs organized in a daily/weekly/monthly/yearly directory hierarchy.

I think many people would be amazed at just how fast their disk can read tens or hundreds of MBs of chat logs; how fast `grep` can find what you're looking for.