What is the best way to write your mega chat?

Question

Chats

There is an idea to write a super mega chat with all sorts of goodies, up to a maximum of 500,000 visitors, but most likely there will be about 150,000. there will be more user pages, profiles, photos ...
The main focus on mobile platforms, probably in most cases will be android ...
General requirements, respectively, that everything be optimized for mobile Internet and for smartphones.
On what to write the server???
The client should ideally be an application for android, and naturally for the browser. Ideally, there should be its own API, but at the beginning it is possible without it.

Answer 1

Don't bother when it's 150k, then there will be money to rewrite it.

Answer 2

erlang-elixir
golang
java

Answer 3

Ideally, you should have your own API, but at the beginning you can do without it.

Sorry, it's too early for you, you just don't understand what you're talking about.
1. Loads are not measured in "visitors", they are measured in rps (reques per second).
2.

super mega chat with all sorts of goodies

it's verbal garbage, it doesn't mean anything. Be specific.
3.

Like a VKontakte chat, with photos and other useful features, i.e. there will be more pages of users, profiles, photos ...

see [2]
In VK, if my memory serves me, in 2010 there were about 10k servers, that's a lot of money, are you really ready to pull this?))
Total 4 units: server, android application, web (public) application, admin application))
First, look towards nodejs, cordova, html5. Just a year later, formulate more specific questions))

Answer 4

[a note of incompetence]
Chat, as I understand it, is asynchrony, which means a node?

Answer 5

VK is written in Node.js

Answer 6

You decided to blind porn chat, or what? :)
With blackjack and courtesans?
Grammar Nazi detected
The easiest way to make a server without experience is on nodejs. But keep in mind that without the experience of creating such software, you are unlikely to come up with something worthwhile.

Answer 7

First, use a ready-made comet server and then, if you don’t like it, write your bike.