This is pretty much as simple as it gets tbh. A couple of web servers backed by a cache/pubsub queue. It may have been possible to do it all in-memory on a sin

This is pretty much as simple as it gets tbh. A couple of web servers backed by a cache/pubsub queue. It may have been possible to do it all in-memory on a single large host, but then if it is unable to meet the demand or fails for whatever reason then you are completely out of luck.