Twitter does not need more than 1,000 employees and could probably get by with <500. They have over a billion dollars in revenue and would easily make a solid profit if they cut staff back to what's actually necessary.
The problem is that they don't seem to have any path to growth. If they slash headcount in half and you've got most of those people dedicated to keeping the lights on then it's hard to imagine a future where they get much bigger and if investors see no path to growth then their stock price is going to take a beating.
[1] https://finance.yahoo.com/q/is?s=TWTR+Income+Statement&annua...
Your math is off by an order of magnitude. Twitter spends >$100M per quarter on stock-based compensation alone. [0] Just what do you think Twitter's major expenses are in "Research & Development" (for example)? I guarantee you that employees are by far their number 1 line item (as they are for most tech companies).
Twitter's Q3 2015 expenses were ~$500M. Do you really think that the majority of that wasn't salaries?
[0] http://seekingalpha.com/article/2253623-twitters-stock-based...
All public companies have to report that stuff and it is usually free to download from their website. It is an incredibly useful skill to learn to read annual and quarterly reports. You can find out if your company is about to tank ;-)
1. User A posts messages either to themselves or by addressing another user.
2. Users B, C, D .. Z subscribe to messages from A and see them on their own feeds.
There are no concerns about message QoS and you don't need a consistency so you can basically blast out messages and if B views it before C then no biggie.
Twitter's basically a pub-sub messaging platform without any kind of need QoS... what am I missing? Why does this require 1000 employees or even 500? it seems like something that could absolutely be run by 50 people with software (feature, optimization) engineers concentrated in one location and operations (test, deploy) teams spread out across the globe at major hot spots. Obviously you also have some stuff like sales and marketing, but I still don't see how that requires 1000 employees.
I don't know about the 500 vs. 1000 employee question, but Twitter is a big engineering challenge.
Nobody's debating that. If it weren't a "large scale distributed system" then the debate would be about 3 employees vs. 10. The core experience without scale could be made by a single engineer.
But running a service like Twitter doesn't require 4,000 employees, even at scale. Facebook has "only" twice as many employees, despite a 10x more complicated product and 12x as much revenue.
Now, I do think there's more to it, once you start adding in monetization and business features, but it doesn't take that many people to run a highly scalable distributed pub/sub.
There were quite a couple of relevant posts on Twitter Engineering Blog if you are interested:
https://blog.twitter.com/2011/spiderduck-twitters-real-time-...
https://blog.twitter.com/2012/blobstore-twitter-s-in-house-p...
https://blog.twitter.com/2014/manhattan-our-real-time-multi-...
https://blog.twitter.com/2014/push-our-limits-reliability-te...
https://blog.twitter.com/2015/building-a-new-trends-experien...
It is not simple but it also doesn't have to be 1000 employee-type of complexity.
As a counter-example I'd point to WhatsApp was handling 1B users with 50 employees. That includes custom apps for fringe phones used in 3rd world countries. It included media sharing, it including managing and ops.
I know they are not Twitter but still 50 vs 1000 is a huge difference.
They've traditionally credited Erlang and FreeBSD as one the techologies that was responsible for their success. Not sure if Facebook will strong-arm them into switching to whatever Facebook is using.
One can then ask, well, why don't companies look at that and learn and do the same? And I think the answer is once they headed in one particular direction with their choices, they are more susceptable to the sunk cost fallacy. Coming in one morning and telling everyone, screw it, we picked the wrong direction 2 years ago. We'll lay off 50% of the people and re-write the whole thing in Swift using this other stack. We'll cut half the products and work on new ones. Etc. That is almost impossible to do. So they are sort of bound to heading in the direction they've been heading, even if individual people will all see it is probably the wrong direction.
Twitter is not an engineering cost first company.
Right, though they retain messages until their recipient comes online.