Most appropriate design for a server that will be accessed very frequently, many computers for a small response?

Question

IIS

Now:
There is IIS and SQL DB. Many computers access IIS every 20 seconds, which in turn accesses the DB, makes a simple request and returns a response to the requesting computer.
Problem:
It worked very slowly and with 300 computers that were knocking on the server, the CPU was at 100% almost all the time (the server is good, it's not in the hardware)
Taken:
All the necessary data from SQL was transferred to the IIS application dictionary and there is a separate task that synchronizes SQL with dictionary. Still not working well enough. With the same 300 connections on the server (not even 300, but much less, because all computers knock every 20 seconds, but each has its own 20 seconds, which means the number of simultaneous connections "blurs"), the CPU jumps to 60%.. .Question :

What technologies exist to solve the described problem and where to dig? Thank you!

Answer 1

If you decide on a node, then this application server can give statics and data directly from memory and access and hold websockets and sse databases and scale to several machines, and even works under linux, windows, mac. On a single i7-2600 Quad-Core class machine, 16 GB DDR3 RAM will give more than 22`000 requests per second with access to the database or more than 50`000 requests per second with cache in the RAM and lazy reading of the database. Withstand 500.000 - 1.000.000 sockets depending on the intensity and configuration of the OS, and more than 1 million SSE connections, they are unidirectional and less gluttonous.
https://www.npmjs.org/package/impress
https://github.com/tshemsedinov/impress
youtu.be/f6McffaVq78
youtu.be/Zr_1YrcXtkE
www.slideshare.net/tshemsedinov/jfwdays-2014impress
www.slideshare.net/tshemsedinov/impress-applicatio...
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