I am trying to make a multi-player game and I wanted to know whats the best way to go about this? The game will need to scan the database continually using a chron job I assume. It may also need to add or remove data based on what it receives. Basically I wanted to know is it a wise idea to set up a database scan for every tenth of a second? Will the computer even be able to process it that fast and modify information once the database reaches 100,000 members?

Does anyone have any experience in this? Is there an article anyone can point me to which would help. I tried searching google but came up with nothing.