DNS

Resolves a hostname to IP addresses; can steer users to regions (geo/latency routing).

Problem it solves: Clients need a stable name while servers and regions change underneath.

Where it sits: Before the first network connection; answers are cached per TTL.

When to use

  • Global traffic steering and coarse region failover.

When not to use

  • Fast failover: cached records keep old answers until the TTL expires.

Failure modes

  • Long TTLs delay failover.
  • A DNS provider outage makes a healthy system unreachable.

Metrics to watch

  • Resolution latency (ms)
  • Cache hit ratio at resolvers
  • NXDOMAIN / SERVFAIL rate

Alternatives

  • Anycast IPs
  • Global load balancer

Configuration in Labs (illustrative defaults)

  • Base service time (ms) = 1 — Processing time per request at zero load. Queueing adds to this as utilisation rises.
  • Health checks (0 / 1) = 1 — 1 = only route to healthy children (failover). 0 = keep sending a share to failed children.

In the guide