dnslisted

# DNS DNS is the global front door: it turns a name (`api.example.com`) into an address *before any request reaches your servers*. It is also a routing layer — the same lookup can hand different clients different answers (by region, latency, health, or weight). Get it wrong and clients reach a dead region, fail over in minutes instead of seconds, or cache a bad answer for hours. It is not a load balancer and not a CDN; it decides *which endpoint a client is told to use*, not how bytes are balanced inside that endpoint. ## When to reach for this A service is reachable by a stable hostname; traffic must be steered to the closest or healthiest region/data center; or an endpoint's IP can change (a new load balancer, a failover site) and clients must follow without code changes. Multi-region or multi-data-center designs need DNS to pick the entry point; single-region designs still need it for a stable, movable name. ## When NOT to Routing *inside* one region — that is a load balancer's job (→ `load-balancing`), which reacts in milliseconds, not TTL-bound minutes. Fine-grained per-request or session-aware steering — DNS answers per lookup, then the client caches it. Fast failover with sub-second recovery — DNS failover is gated by TTL and resolver caching; do not promise instant cutover from the name layer. And do not reach for exotic routing policies before a number shows users are spread across regions (YAGNI) — a single `A`/`ALIAS` record is the right default for one region.