&gt;  It doesn&#x27;t store them, and it certainly doesn&#x27;t, say, try to make them available in a searchable away to everyone in the world.<p>Back of the envelope calculation: If your messages are 256 char messages, on a 128GB ram server you can fit 500 billion of them in memory; incidentally, that&#x27;s one day&#x27;s worth of tweets these days. I recently got a quote for a beefy 256GB ram server from Dell for $6,000. To make things easier, let&#x27;s assume $10,000 with redundant 1TB SSD and everything else you might need. The data is extremely easy to shard.<p>With proper caching, you can probably keep 99.9999% of all tweets shown in just one such servers, and serve them within a few ms. I don&#x27;t have recent experience with web frontends, but a properly configured nginx could probably server on meager hardware can do a few tens-of-thousands requests per second. a Seastar server on beefy hardware can probably handle a significant percentage of Twitter&#x27;s load.<p>Search is a little harder, but not by much.<p>Is this engineering trivial? Far from it. But I&#x27;ve worked with stunt programmers who can build this in a few months with a 3 person team. At least one of them commands a salary of about $500K last I heard.<p>Is that all Twitter is doing? No, I&#x27;m sure they have 10 backend &quot;things&quot; for every user visible &quot;thing&quot;. They needed something like Bootstrap for <i>internal</i> use, after all. I don&#x27;t really believe you can run Twitter with just $1M&#x2F;year in capex, just $1M&#x2F;year in opex and just $1M&#x2F;year in engineering salary - you need a whole lot more than that; In fact, to pull in revenue of $2B&#x2F;year (which Twitter seems to be on track for), you probably need 50 people just in accounting.<p>What I am saying, though, is that the technical challenges faced by Twitter (at least those that are visible to users) are highly overrated. If you know what you are doing, Twitter can be run on $50,000 worth of hardware; This has been true since 2007 - Computers were weaker and had less memory then, but Twitter had much less traffic too. I&#x27;ve looked at the numbers every single year since 2007, and at any point in time, the &quot;bare bones essential hardware for interactive response&quot; was in the $50,000 range. Which probably means if they spent more than $1M&#x2F;year on hardware (or depreciation-equivalent-hosting) at any point in time, they should have hired better engineers.