[pdimitar]

> Once you start to scale, the bottleneck is rarely the application layer. For the typical crud web app it's likely to be the database.

You seem to be downplaying the importance of an efficient app layer and I respectfully disagree.

1. Using well-optimized tech for the app sends you right at the DB scaling problems phase, so you never go through the "our app layer is too damn slow" phase -- which can kill a startup pretty damn quick (and history knows examples). So, it's a huge win in my eyes.

2. Most apps never even take off to the point where the DB is the bottleneck so a strong app layer is a godsend; I'd estimate 80% of the apps struggle with optimizing backends and caches and not DBs -- at least judging by my 15 years of career which, I admit, is anecdotal evidence and doesn't mean much.

3. Those apps that do scale that far are very grateful to their backend engineers who spared them all the "tune our Java / Ruby / PHP / Python VM's memory usage and GC behaviour parameters" dance (and that dance can last for weeks and weeks almost without sleep!).