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Comment by lotso | Hacker News Reader

>However of all the various applications you could conceivably scale to hundreds of millions of users this is one of the simplest. I do not think acknowledging that is cringeworthy at all.

What other apps besides social networking and communication apps even get to hundreds of millions of user?

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I guess "users" is a confusing concept, but a service like Cloudflare would be an example of a more complex application serving that scale of people.

Is cloudflare more complex or less? If I'm connecting through a CF proxy in North America and someone else is connecting through Europe, there's not really any state that needs to be synchronized between us. If I send a message to somebody in Europe, that obviously does need to be synced.

Actually there is state that might need to be synchronized between the two locations. The cached state of the page or other resources there. CF doesn't just do a blind proxy to the host, along with that it does a number of checks for common attacks and other misbehaving clients.

The NA data center can't decide how long to cache a page without consulting EU (and Asia, and SA, and etc.)? Obviously there is some shared global state (how else would each endpoint know where to proxy to?), but it seems unlikely every request passing through CF is mutating the same global database.

Having tossed the towel in trying to build a global CDN/caching system with relatively few endpoints some years ago, I can tell you that it's very complex. I can't speak to the complexity of something like WhatsApp, and so any comparison would be totally ignorant and anecdotal, but I am guessing that CloudFlare is orders of magnitude more complex than WhatsApp.

Search?

Photo and video sharing/storage apps with the problem of storing huge amounts of data + most of them includes the communication part too (comments). If I remember correctly WhatsApp doesn't even stores the text messages.

There's still a big difference between WhatsApp and the likes of Facebook when it comes to complexity. Last I checked, WhatsApp does not do face recognition, to pick an example at random.

I'll wager the complexity of WhatsApp is not 1% of 1% of Amazon.

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