What is the best way to write a highly loaded application?

Question

Highload

It is necessary to write a highly loaded web application (ad network). What tools would you use to implement the server side of such a project if the application has more than 1 million simultaneous connections, that is, the total number of simultaneous requests to display ad blocks from users?
The main task is to ensure stable and uninterrupted operation of the application at peak loads, as well as the possibility of application scalability.

Answer 1

Well, the node is praised for asynchrony and loads ... But in general, can C ++? With straight arms it will be exactly fast.
But to be honest, the question is vague and there are many nuances... First of all, the main problem will be balancing.

Answer 2

if the application has more than 1 million simultaneous connections, what is the total number of simultaneous requests to display ad units from users?

If we consider realistically - only horizontal sharding.
If "sparrows" - at the same time 1 million connections - this is fantastic!
In general:
1. we put the statics into the Opcache RAM, or a microservice in C, or we load it into Redis and from there we already give it away.
2. in the JS-code of the widget - only AJAX call to the service to request the banner ID-shnik.
Here on this you can make statics by IDs from the database: webd.is