LoverpingerA name needs an address.
DNS lets applications discover the network addresses associated with a domain name. A resolver may answer from its cache or follow the DNS hierarchy to find a current response. These two situations can produce different timings.
A shorter TTL is a trade-off.
A time-to-live tells a cache how long it may retain a response. Lowering it can help a planned address change propagate sooner, but it also increases the need for fresh lookups. It does not close existing connections or guarantee immediate switching by every application.
Measure the right thing.
Compare cold and cached lookups, record the resolver and test from the locations your users actually use. A resolver that is quick from one network may behave differently from another.
Treat DNS changes as an experiment: record the previous values, wait for relevant cache lifetimes and verify the application after resolution succeeds.