If starting with WP is faster, do so. Assuming you'll have some form of business model way before you get to 180M users, you'll probably want to switch at some point. It won't be an issue, focus on scaling to 100k users first ;)

Otherwise, the math is pretty easy. The key questions are: how many requests per user per session, how many request per user per minute, and how many request per second can the hardware serve?

Supposing an even distribution of 180M visits per day and 1 requests per visit:

  125,000 visitors per minute

  125,000 http request per minute

  2,083 requests per second

That should be doable on a large vps of some sort, even for wordpress.

Now the question is, how complex is the workflow? Certainly a visit will consist of more than one request. Also, visitor frequency will most likely peak during certain periods of the day/week.

tl;dr: yes.

http://reviewsignal.com/blog/2016/09/14/500month-enterprise-...

if it's static cache hits, tons of companies can do 5000/second without issue.

It looks like the guys at WPEngine have written an eBook about scaling WordPress if you want to check it out: https://wpengine.com/resources/scaling-wordpress-high-traffi...

I just skimmed their book. Seems mostly useless. No mention of load balancing. No mention of memcache, etc. etc.

WordPress itself, as in the source code, can definitely handle however many visitors gets thrown at it. Where you'd have to scale is the amount of RAM where your website sits. I've been pretty successful with testing 10,000 visitors over a minute period on 512 MB of RAM without issues, though I recommend you have at least Memcached installed and enabled.

If you're talking about 100,000+ visitors, than you'd probably want to get some good advertising and update your RAM.

This is definitely premature optimization. Somewhere between zero and 180 million, the decision on how best to optimize will be much easier to answer.

Focus now on getting lots of uniques.

With caching proxies and load balancing and whatnot, Wordpress can scale to whatever number of viewers you may happen to have.

What Wordpress may not scale to support easily is the complexity of features that a site may have accumulated by the time it gets to 180M users.

Do you even need to worry about that many? I don't mean to sound rude, but I doubt you'll ever hit 180M

Startups need to worry about scaling.

No, startups need to worry about surviving the starting up phase and getting to the 10000 users stage.

The few 10000 users companies then need to worry about getting to the million users stage.

And so on.

I just saw that sites like TechCrunch are built using WordPress. If one of the top 1000 visited sites in the world can use WP, its likely that it is able to serve a large number of people.

I believe it's hosted by https://vip.wordpress.com/

The short answer is yes. That being said, you have to ask yourself if that's the most pressing issue your site has. Almost certainly it is not.