DNS connection pool cold start

A Node.js API that calls an internal pricing service starts adding intermittent +20ms to +300ms to a fraction of requests, in waves. The slow time is all spent before the first byte of the outbound HTTP request is sent, the pricing service reports fast service times. CPU/memory fine. The recent change: a refactor replaced a long-lived HTTP client (keep-alive, cached connection) with a fresh fetch/request per call to a hostname like pricing.internal.svc. Your internal DNS is healthy and not erroring. Conntrack and ephemeral ports are fine. How do you triage and what's the fix?