How does Stack Overflow keep track of the number of questions under a tag as well as the number of votes, views, answers per question, etc? I'm just eager to know if they maintain a separate table or do a count query every time.
Not quite a duplicate, but a fellow MSO user posted an interesting writeup about this at Dissecting the Stack Overflow views counter. Excerpt:
The last part of the URL - a947 - seems to be dynamically generated. It is changed every 15-20 minutes and is the same for all questions and presumably users (I tried anonymous access, changing my IP address, it stays the same during the interval).