Reddit needs 300 people max to run, and they got like 1500.
It'd pretty easy to be a profitable company with a $10 million turnover, but you're not going to be a unicorn this way. Founders and VC wants high return on their equity, and today being enormous without profitability is valued more than being reasonable and profitable.
There was once an age where investors would buy in simply on the belief of unicornedness, but that ship sailed several months ago. Investors have become much more critical of tech businesses, showing substantially less interest in tech companies that aren't displaying strong fundamentals. A recent Fidelity report indicates Reddit's own valuation has dropped by 41% on that change in sentiment.
In fact, if profitability was the goal, then he should have been ousted at this point, because he's been back for 8 years now without succeeding to make the company profitable.
I don't think he is that inapt, and that his board is stupid to let him in charge despite such a failure, profitability was just never the goal. Getting the biggest possible IPO is the goal, but the timing is actually very bad for them for the reason you mention and now they're trying as hard as they can, including by creating fake subreddits with translated old content for non-English speakers (at least French and German speakers).
Just fyi, reddit rose around the same time as Facebook so it’s likely they share a similar governance model, where founders control an outsized part of the board/voting shares. Since Uber and wework semi-imploded investors are less forgiving of that sort of thing but legacy companies like Reddit likely still are run that way.
There is no reason reddit can't be profitable if they did these things. They don't need 100,000,000 users watching videos to bring in ad revenue. They need 10,000,000 users generating good content that ends up as top google results and they can find clever ways to monetize product tie-ins, annual meetups (those were a thing in a lot of cities a while ago), events, merch, and subscriptions. It isn't rocket science. The top stockholders just have to be satisfied to be millionaires instead of billionaires.
But did they try to be?
The feeds are definitely not cacheable (except for maybe on a per user basis with a low ttl). Popular and all are never the same upon reload. And every user is going to have a different combination of subreddits. Those feeds have to be generated on the fly. Most of the data is too dynamic and ever-changing to cache effectively.
Also a lot of their content is not "hot" and "commentable" anymore.
- Cache of most popular topics (again, even a 10s invalidation time) would help
For the logged users you could do something more dynamic, for example, cache the front-page snippets of the main subs + add the ones for the user. And again cache that
(unless the 'new reddit' makes this harder, to which I would say - well deserved! ;) )