This is why I don't like health related business models. In a similar scenario, who's stopping Susan from sueing over a "bad" outcome from the platform recommendation. When people's health is on the line, shit can get ugly really fast.
My experience with SSE so far (take this as recommendations if you wish)
You need to implement a server-side heartbeat feature.
You need to handle the close event from EventSource and be able to reconnect.
Tabs can be problematic. When you subscribe, you use a URL with a nominal ID to identify the client. For example, on a chat app, you would use /api/sse/userA/subscribe
Problem is, if userA starts opening tabs, each tab creates a new subscription for userA so you need to randomize each connection (userA-UUID).
If you don't use a nominal id, the server won't know to which subscriber to send the data and you don't want to broadcast all your chats.
I've used the Broadcast channel API in conjunction with SSE to have only one tab handle the SSE connection, and broadcast incoming SSEs to the other tabs which also reduces the number of connections to the server to one.
On the server it's also a PITA because not all instances/pods have the subscribers list. The way I've found to solve this is with clustering the instances with Hazelcast or Redis or a MQ.
But once you figure out all this, SSE works quite well.
IMO, LC (and similar) aren't a bad choice for the interview process. The problem comes when it's used as a silver bullet solution. Most seniors that'll show up to an interview are probably working and simply don't have the time or will to grind LC.
Also, SWE is a highly movable profession, where being more than 5 years on the same place is unusual. So every ~5 years you have to polish your CV, grind LC and basically restart learning all computer science concepts you haven't used in those ~5 years, without feeling burnout or dismay.
Funny thing is that A players can go downhill not because of their engineers, but because of their management. How many companies have we seen in tech go under because of bad engineering vs bad management?
End of day you have to deal with physics. All those bits have to be stored somewhere. Have we really reached the point where the Facebook database can be stored in a distributed system across personal devices? Hell no! As a matter of fact, being centralized, FB can store that amount of data more efficiently than any Blockchain can even dream about.
There are this things called "Exchanges" in every airport in the world.
With the US dollar, Euro and some others, the world is your casino (following the comparison) and you can trade all of them. Same with gold and silver (although this are a bit harder to trade).
Hell, try to pay a taxi in Djibouti, Sao Paolo or Islamabad with a BTC or USD and see which they'll accept and which will get you kicked out.
I don't remember where but a guy made the comparison between NFT and those companies that sell stars, or land in Mars or the Moon, like they'll sell you a paper that says you own Proxima B.