I spent a lot of time on IRC in #level8, but people were good enough to not just post the answer. Somebody let me bounce my ideas off of them, and they helped me just step back and think clearly, which was all I needed to get it.
Most of the time, folks on IRC made this sound way harder than it actually was (my mistake!). That threw me off as I started premature optimizations with threads, pipelining and multiple async webhooks. Spent a lot of time there, and eventually I couldn't get it working on the production machine. Then I just wrote the 'naive' solution and that just worked fine.
I saw the full solution (not the code, of course, but the idea) posted in #level8 several times when I was hanging out there on Friday. There was also another channel called #level8spoilers or something that posted the full solution with even more frequency.
