[svennek]

If it is readonly shared-nothing queries, I am sure the hardware I have in my flat can do that as well..

The hard parts are updates in a shared system with a single consistent "view" requirement..

[why_only_15]

The hardware in your flat definitely cannot do 1 billion queries per second -- that requires a massive, global system, which can probably also support a shared system with ~100,000x less queries.