Tech & Computing riddle: Opening a new one each time is ruinously expensive, so I keep a small set and lend them out. Run out and everyone simply waits — politely, invisibly, and for a very long time.

I hold nothing of my own, yet almost everything passes through me. When I run out of room I forget the oldest thing first. You only notice I exist on the day I am wrong.

I make finding fast and writing slow. I am useless when you do not know what you are looking for, and I take my fee on every single insert.

Add more of me and the work finishes sooner — until it does not. Past a certain number I spend more time coordinating than working.