I have a few questions about the Ktor HttpClient on JVM, I'm using the default engine ATM, but I'm not bound to it. • May I use the same HttpClient from multiple threads at the same time (connecting to the same server)? • If I use the same client from different threads at the same time, will cookies be synchronized? • How many clients may I have active at the same time (100+ would be good for me, these go to different servers).

May I use the same HttpClient from multiple threads at the same time (connecting to the same server)?

Yes.

If I use the same client from different threads at the same time, will cookies be synchronized?

If you would use the

HttpCookies

plugin then yes.

How many clients may I have active at the same time (100+ would be good for me, these go to different servers).

I think it depends on the particular resource constraints.