bsimpson63

https://grafana.com/ for the graphs and https://www.draw.io/ and http://www.fiftythree.com/ for the diagrams.

Not having to implement redis ourselves.

> keeping it in RAM on a single machine

> 500kB packed array, coupled with cooldown logic, should have a negligible performance cost and can easily be done on a single thread. That thread could interact via atomic channels with the CDN

That's not simpler.

We used tools that we're already using heavily in production and are comfortable with.

What was wrong with it?

You're basically describing how we used redis for this project.

This was just a back of the napkin estimation. I think at one point we calculated that we'd be able to support one tile placement per user per second.

At reddit it's much easier for us to stand up a new Cassandra column family than a new postgres table (not saying this is how it should be, but just how it is).

All we needed to do here was add some simple locking and we would have been fine.

That's actually how it works. If you target an ad to /r/programming it will show up on the frontpage for users subscribed to /r/programming.