I imagine you've never actually had to solve any of these hard problems, which is why you think it's so easy to do.

That's bordering on (if not crossing into) ad-hominem.

There was no accusation of "so easy", only so not expensive and supposedly (and previously, demonstraby) solved in the last 30 years.

They may well be "hard" or even "expensive" for some definition of those two words, but if it weren't, it would defeat much of the (stated/advertised) purpose of outsourcing/cloud.

You propose just to buy servers in 2 locations to keep Slack services up? Doesn't work, when you need to store gigabytes daily and have dozen thousand reqs/sec synchronized.

Geodistributed datacenter requires multiple direct low-latency multigigabit/sec connectivity, special software to manage, test and check it, skilled devops.

I know. there's totally not a command called rsync. And "replication" is just a word you hear on star trek along with teleportation.

Although I agree with your premise, I think the delivery takes away from your point a bit.

Specifically, you risk people piling on that rsync isn't good enough in the modern world and referencing the comment criticizing Dropbox as being little more than an rsync replacement [1].

Of course, the specific tool one uses is irrelevant. The data synchronization problem may not be well solved, but it has been very well studied, with a remarkable number of good-enough options.

So, no, there isn't just one "sync" button, as the parent comment snarkily suggested, but there may be two, one where you might lose the last N seconds of chat (perhaps temporarily) and another where you lose the ability to chat entirely for those N seconds.

[1] Although it had other criticisms, such as monetization, which are, naturally, ignored.

Oh, yes, someone in Slack clicked the button “Pause” and we all are waiting, when Slack’s hero will click “Resume” :)