Not being a dick here but is this not a fairly obvious flaw?
I mean why not keep a structured "message log" of all channels of all time ?
For every write the system updates the message log.
I am guessing and making assumptions I know.
Having worked on other messaging apps, these are usually separated because their performance/scalability requirements are different
Agree with this point of view. Except the Jabber/XMPP Cisco legal thing, there's just no tech answer on why on earth Slack did not use XMPP under the hood.
Slack would have known about WhatsApp architecture because it was widely talked about pre-FB acquisition (2014).
And Slack was founded in 2013.
Sometimes it's for OKRs and power/politics balance between departments and teams in an enterprise. "If an existing tech like XMPP is used then no serious development could be needed" fear (which is not really true). It can lead (and leads) to a huge waste of resources and overspending.
But it's a bit similar to building a luxury house. Not because an owner needs it. But because he can afford it.