It's true, and the RPC comment is also very plausible
It's definitely not as ridiculous as what lots of experienced engineers are oddly saying
e.g. simply open up Twitter in Chrome's devtools and look at the networking tab -- I get 148 requests that finish in 6.3 seconds
That is very plausibly "1000 poorly batched RPCs" that makes Twitter slow in other countries -- if it's 6 seconds for me, it's easily 20, 30, or 60 seconds for others
It will be shocking to me if some executive attention on latency can't halve it, in short order. The problem with latency is that no one team is in charge of it -- every team is incentivized to use as much latency budget as possible to ship their feature.
Larry Page harped on at this at Google for a decade, until he kind of gave up / moved on, and Google became nearly as slow as every other website.
So Elon is absolutely doing the right thing with respect to latency -- he's not wrong, and he's not micro-managing.
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Yes Elon is not infallible -- he made flatly wrong claims about self-driving for years, despite experts in the field telling him otherwise, to his financial benefit. And Tesla is being rightly investigated for those claims (years too late, probably)
It doesn't mean that Twitter isn't slow as hell for extremely basic reasons