I’d say that Reddit’s been pretty reliable for some years.

When they were scaling up, there were points where it was a lot flakier.

I think that that part of it was more testing before stuff went to production. Also, they have a lot of publicly-visible monitoring stuff now that didn’t exist when it was young, and I’m pretty sure that they have someone who gets notified immediately if one of various things breaks, since they started putting up a message quickly when something broke with a quick summary and giving an ETA on a fix; their time to get stuff fixed also fell off. The early days, I remember things not infrequently breaking for a day or so.