How are type-ahead web text boxes done these days?


New member
I've seen these becoming more prevalent these days and they seem to have a very good response time. If you look at Google or the post searching by username on here, they start populating a faux drop-down list as you begin typing in the text boxes.

Are they just continuously making asynchronous web service calls to populate these drop-downs as you type? I'd be afraid that would cause too much web and database traffic if I implemented something like that on my company's application.