>'Isn't that comparing apples to oranges?' On another site, in another context, it probably would be, but here it's really presented as a contrast of scale-up

>'Isn't that comparing apples to oranges?' On another site, in another context, it probably would be, but here it's really presented as a contrast of scale-up versus scale-out - something the regular audience of highscalability will certainly grok. In context... 'Stack Overflow still uses a scale-up strategy. No clouds in site. With their SQL Servers loaded with 384 GB of RAM and 2TB of SSD, AWS would cost a fortune. The cloud would also slow them down, making it harder to optimize and troubleshoot system issues. Plus, SO doesn’t need a horizontal scaling strategy. Large peak loads, where scaling out makes sense, hasn’t been a problem because they’ve been quite successful at sizing their system correctly.' It's an acknowledgement of their relatively unique strategy and the short list of caveats that make it possible.