Running the Pocket OWL web server was free.
It runs on Google App Engine. Google App Engine is basically a big "farm" of computers that you can rent time on. But if your program doesn't demand a lot of "thinking", then it runs for free.
I was pretty sure that the OWL could run for free. ~80 teams, each interacting with the site a few times every few minutes, keeping track of their state with less than a billion puzzles... It's a big game, but a small computer task. One computer could handle our load with one CPU tied behind its back.
But I wasn't sure, of course. Maybe I'd underestimated. Or maybe we'd make some last-minute programming error so that some common action made the computer think really hard. So I handed over my credit card number to Google and agreed that if the OWL went beyond the free usage threshold, I'd pay for the extra.
We didn't go over the threshold. And unfortunately, I didn't think to look at the app dashboard until after midnight, and its quota display resets at midnight (apparently). So I don't know how close we came to the threshold. But here's a pretty QPS graph:
So that was the view a little after midnight. You can see that people start signing in around 4:00 in the afternoon; demand was usually around 1 hit every 2 seconds; occasionally getting a little higher than 1/s. Things calmed down after 10pm.
As I write this, it's the day after the hunt. Our CPU usage is about 6% of the daily free quota. Just a few teams are interacting with the server. By straight extrapolation, you'd think that we couldn't possibly have stayed under quota yesterday afternoon. So I guess straight extrapolation doesn't work so well here.
Oh well. Next time, I'll know to look at the dashboard before midnight.
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