[jbert]

One difference is in "dead connection detection". How do you know that your AMQP connection is down? At some level you're polling, whether that be TCP keepalive, application keepalive or something else.

If you're doing polling, you're actually back at the same pre-webhook place - polling their server on some timescale which is a compromise between latency and load.

Yes, a TCP keepalive is generally cheaper than an HTTP long poll request, but only by a constant factor.