Even 0-RTT connections still allocate connection state. IPFS learned this the hard way.

The mental model you need is the attacks that cause the Linux kernel to send SYN cookies. Learn how that attack works and you'll understand why you can't have connection state here (and neither does the Linux kernel during a SYN flood).

https://en.wikipedia.org/wiki/SYN_flood

https://en.wikipedia.org/wiki/SYN_cookies

It's much worse for DNS-like services, which is why after all these years DNS still uses UDP. Imagine if the root zone servers had to allocate connection state!

But it all depends on what you're using the DHT for. If you've decided "let's write a DHT that won't be used for naming or DNS-like purposes" then you'll probably get away with it.