Hard to believe, but yeah possibly
Site Server Problems - Possible Solution Proposal

Even much larger companies with vastly larger technical and financial resources, have issues at times.
Ok, but at the end of the day it's a chess site. You have a database with player profiles and you have to transmit single moves and a clock... these are problems businesses had solved, what... 30 years ago?
Chess.com bought Play Magnus for almost 100 million. We can't sit here and pretend hosing 100k chess games is just too difficult for a company with that kind of money.
It takes a lot more than that to run any site that is large enough.

Even much larger companies with vastly larger technical and financial resources, have issues at times.
Ok, but at the end of the day it's a chess site. You have a database with player profiles and you have to transmit single moves and a clock... these are problems businesses had solved, what... 30 years ago?
Chess.com bought Play Magnus for almost 100 million. We can't sit here and pretend hosing 100k chess games is just too difficult for a company with that kind of money.
It's not money, it's computer power that's the issue.

It's scaling and the fact there's a lot more than just playing games going on.
Eh... what do you mean? A news section? Streaming? Anything that hasn't been been in industry for over a decade? I don't see this as a particularly challenging business in terms of coding. Lichess has done it as a non-profit. I don't get it.
Forums, blogs, clubs, news sections, streamers, puzzles, achievements, socials, new accounts, cheat detection, analysis, the list goes on.
Lichess offers considerably less than chess.com and also has a considerably smaller player base.

It's scaling and the fact there's a lot more than just playing games going on.
Eh... what do you mean? A news section? Streaming? Anything that hasn't been been in industry for over a decade? I don't see this as a particularly challenging business in terms of coding. Lichess has done it as a non-profit. I don't get it.
A serious 👍for lichess

Even much larger companies with vastly larger technical and financial resources, have issues at times.
Ok, but at the end of the day it's a chess site. You have a database with player profiles and you have to transmit single moves and a clock... these are problems businesses had solved, what... 30 years ago?
Chess.com bought Play Magnus for almost 100 million. We can't sit here and pretend hosing 100k chess games is just too difficult for a company with that kind of money.
It's not money, it's computer power that's the issue.
Yeah but technology should have such handled

It's scaling and the fact there's a lot more than just playing games going on.
Eh... what do you mean? A news section? Streaming? Anything that hasn't been been in industry for over a decade? I don't see this as a particularly challenging business in terms of coding. Lichess has done it as a non-profit. I don't get it.
Forums, blogs, clubs, news sections, streamers, puzzles, achievements, socials, new accounts, cheat detection, analysis, the list goes on.
Lichess offers considerably less than chess.com and also has a considerably smaller player base.
Interesting

A serious 👍for lichess
Not really. The reason Lichess CAN do it as a non-profit and chess.com cannot is because Lichess lacks a huge majority of the polish and services offered by chess.com, and has a much smaller player base. I can guarantee you Lichess would not be able to survive as a non-profit if they tried to do what chess.com does

Yeah, but the only thing I can think of that Lichess offers that chess.com doesn't offer for free is a game review.. and even that's much lower quality and running on a lower level stockfish.

Ok, cheat detection is definitely its own thing.
Puzzles are just an easier version of games, although mining unique puzzles from your database could be an interesting ongoing project, since not every tactic is something a human would consider worth reviewing, and even then not every business would consider worth publishing (even "hard" puzzles online are conceptually easier than ones found in books. I don't know if that's deliberate or not).
Forums, clubs, blogs, and news are small parts of the site most don't visit, and are structurally the same.
Structure isn't the point, it's server space.
A couple hundred public forums and who knows how many forums being made in thousands of clubs literally every day are definitely something that requires a good chunk of server space. While Lichess apparently has a forum system there's definitely not as much activity there as there is here. There are streams, interactions, daily games, tournaments, and so many other things that require space on a server.

Lichess has a much smaller player base.
So it's about a 1:2 ratio.
I've seen lichess handle over 100k players plenty of times.
I think we would need more of an average before we start comparing these numbers.

It's scaling and the fact there's a lot more than just playing games going on.
Eh... what do you mean? A news section? Streaming? Anything that hasn't been been in industry for over a decade? I don't see this as a particularly challenging business in terms of coding. Lichess has done it as a non-profit. I don't get it.
There are numerous sections of the site all with related database tables being accessed all the time by hundreds of thousands to millions of members all around the world at any given tine. There are periodic processes that run to generate things like statistics and insights, chats, forums, blog posts, events, etc. It isn't just sending and receiving a few moves around.
I don't know how large the code base is but I would guess it's likely millions of lines of code, hundreds of servers and compute instances, quite a few database with millions, hundreds of millions, billions, and in some cases trillions of entries. Firewalls, load balancers, network equipment, various ancillary software pieces to manage, monitor, and support it all.
Yes, it's all been done and being done and any enterprise of any scale has to deal with a lot of things. If you've never worked in any company that has a large IT type footprint, it's not terribly obvious what it actually takes.
As to the non-profit, there's still a lot of that same stuff, being supported by funding and vilunteers. Pretty sure that chess.com is probably at least an order of magnitude larger in needed infrastructure and resources, just for the main site.

Oh, and their FAQ was written by someone who (apparently) has English as a second language (and didn't learn it until their 30s).
And look, if you didn't learn English in school like most of the world, that's fine. I think it's great chess.com (apparently) hires poor villagers in the middle of nowhere... just, you know... maybe don't have that particular person write documents in English that people will read.
Seriously. Take on a single chess-loving intern for 1 week and have them rewire all of it. It wont be worse, I promise.
Documentation grows with the site and is touched by a lot of different people throughout the years. Pretty sure the staff member keeping support articles current is a native English speaker.
The site does have employees from all over the world.
I would imagine with the amount of profit gained they have plenty going to provide the best options for whatever is technically needed to keep cc running smooth, you'd think.
The site invests heavily into infrastructure and updates. There are a lot of things that can cause issues, such as the aforementioned DDoS attacks, code updates that have bugs or scaling issues, a lot of unexpected and legitimate traffic. Businesses plan for unknowns but even if you over architect (with a lot potentially wasted resources) you can get hit by something that exceeds anything you thought was possible.
Even much larger companies with vastly larger technical and financial resources, have issues at times.