[mbell]

The article said they could rebuild the count if they needed to. So something in regards to each click is being stored. If you were using postgres you'd just setup a trigger on that table to increment the click values (stored in another table) as appropriate. No aggregate function needed.

[samstokes]

Certainly you can implement this same pattern without Redis. Triggers in Postgres would be a reasonable way to do it. I didn't say you can't do this in Postgres, I said you can't do it with COUNT().

It does indeed sound like they're storing every click: that's precisely why using aggregate functions would be expensive.

[guywithabike]

You absolutely can do it without COUNT. Just increment a counter value, the same way they're doing it in Redis.

[pestaa]

Why was this downvoted? Adding 1 to any number field is just as an atomic operation as incrementation is in Redis.

[samstokes]

Presumably it was downvoted (not by me) because it's refuting a claim I didn't make:

samstokes: I said you can't do it with COUNT()

guywithabike: You absolutely can do it without COUNT

Then we agree.