Basically nothing I have ever used had 99.99% uptime except maybe the phone and emergency services. Why do you need this level of uptime unless life and limb depends on you?

My bank has regular scheduled downtime, Steam/Dota has regular downtime, entire Microsoft datacenters had issues and had around a day of downtime, Lime, Uber, my mobile carrier - all had downtime or bugs or glitches that were equivalent to downtime.

If you really need crazy uptime, then you must make sure you have no bugs, because bugs cause more downtime than any hardware failures.

That means an approach to software development that isn't relying on flavour of the month js library.