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Module 4 · Edge: DNS, CDN, Load BalancersDay 03020 min

GeoDNS and DNS Load Balancing

Use DNS to send users to the right region.

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Day 030

GeoDNS and DNS Load Balancing

US user
client
EU user
client
GeoDNS
edge
US region
service
EU region
service
Signal path
GeoDNS returns region-specific IPs
US user
client
flow
GeoDNS
edge
EU user
client
flow
GeoDNS
edge
GeoDNS
edge
flow
US region
service
Memory hook

GeoDNS and DNS Load Balancing: use dns to send users to the right region

Mental model

move the first decision closer to the user

Design lens

DNS traffic split is approximate — caches deliver in chunks.

Recall anchors
StrategiesLimits

Why it matters

GeoDNS returns different IPs based on the resolver's location, sending each client to a nearby region. It's coarse (per resolver, not per user) but cheap and effective at the global level.

Deep dive

Latency-based routing measures resolver-to-region latency and picks lowest.

Weighted routing splits traffic by ratio — useful for canary or migration.

Per-region health checks pull dead regions out of rotation, but TTL bounds responsiveness.

Demo / scenario

Migrate 10% of US traffic to a new ECS deployment.

  1. Add canary record at 10% weight.
  2. Monitor SLO/error rates.
  3. Increase weight as confidence rises.
  4. Roll back fast: weight=0; old TTL ≤ 60s.

Tradeoffs

  • DNS traffic split is approximate — caches deliver in chunks.
  • Doesn't handle individual user stickiness.
  • Use anycast/L7 for finer-grained control.

Diagram

US user
EU user
GeoDNS
US region
EU region
GeoDNS returns region-specific IPs.

Mind map

Check yourself

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Sources & further reading

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