Perhaps we can debate whether this is really a Rails-specific problem per se, but we definitely had lots of problems scaling to prevent long-running IO from sat

Perhaps we can debate whether this is really a Rails-specific problem per se, but we definitely had lots of problems scaling to prevent long-running IO from saturating web/job worker pools for things like taxes, shipping rates, syncing external inventory, ad syndication, etc -- anything where we had to make multiple network calls to the outside world from a Rails thread was a big pain.