I worked at a place where I can say, FusionIO saved the company

The slightly better solution for these situations is to set up a reverse proxy that sends all GET requests to a read replica and the server with the real database gets all of the write traffic. But the tricky bit there is that you may need to set up the response to contain the results of the read that is triggered by a successful write. Otherwise you have to solve lag problems on the replica.

You can get up to, I think, half a thousand cores in a single server, with multiple terabytes of RAM. You could run the entirety of Wikipedia's or Stack Overflow's o Hacker News's business logic in RAM on one server, though you'd still want replicas for bandwidth scaling and failover. Vertical scaling should certainly get back in vogue. Not to mention that individual servers, no matter how expensive, cost a tiny fraction of the equivalent cloud. Remember the LMAX Disruptor hype? Their pattern was essentially to funnel all the data for the entire business logic onto one core, and make sure that core doesn't take any bullshit - write the fastest L1-cacheable nonblocking serial code with input and output in ring buffers. Pipelined business processes can use one core per pipeline stage. They benchmarked 20 million transactions per second with this pattern - in 2011. They ran a stock exchange…