[lotyrin]

It sounds like the product is already a proxy (Websocket -> XMPP) so I'm not sure what exactly they're deploying multiple times per day.

It also seems like they could have done simple blue/green and extend their websocket protocol and client to support a hand-off "hey, there's a new version of the proxy, reconnect in x seconds" message (and have idempotency of messages) such that they could have a rather smooth schedule where everyone can reconnect then disconnect gradually over some period of minutes instead of hours and not have either sudden spikes or any period of interruption for clients.

[ah-]

Or just a generic reconnect in case the websocket connection breaks for any reason really.

[lotyrin]

That would require an interruption in service between the server closing the old connection and the client reestablishing a new one, which they sought to avoid.