In the midnineties I was hired to improve the performance (and eventually rewrite) a custom in-house search engine. I dipped into the software and there were some quick wins, but I couldn’t get the damn thing to reply quicker than 100 ms. In desperation I just grepped for the number 100 and sure enough I found a 100 ms sleep in the routines handling the connections. Turned out the author had made a mess of his socket handling and by trial and error had found out he could get the thing to work reliably only by waiting for a while.