Tyk doesn’t explicitly cache DNS data, it hands off to golang’s net/http library which handles the eventual call that goes out, which includes a resolution step AFAIK, looking around I can see that apparently they do not do any caching.
Do you have Tyk explicitly closing connections (it’s an option in the tyk.conf) - it might be re-using an existing TCP connection and recycling for further requests?
I can’t speak to this, this sounds essentially like DNS load balancer, so the resolution should just round robin at the DNS level, not at the client level?