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Route 53 AWS's DNS service — also handles failover and traffic routing
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Route 53 is AWS's DNS service. You buy domains, create hosted zones, and add record sets (A, AAAA, CNAME, TXT, MX). Beyond basic DNS, it supports routing policies: simple, weighted, latency-based, geolocation, and failover. Health checks integrated with routing let you direct traffic away from unhealthy endpoints automatically.
GOTCHA DNS caching is ruthless. Even if you change a DNS record instantly, clients and intermediate resolvers won't see the change until the TTL expires. For failover scenarios, set your TTL low (60s or 30s) — but that increases query volume and cost.
HOW ROUTE 53 RESOLVES A QUERY
01 Client queries `app.example.com` — their resolver asks the Route 53 authoritative name servers.
02 Route 53 checks the record set. With latency-based routing, it knows the user's region and returns the IP of the fastest endpoint.
03 Health check before returning, Route 53 verifies that the selected endpoint is healthy. If not, it returns the next best alternative.
04 TTL the response includes a TTL (default 300s). The client's DNS resolver caches the answer until the TTL expires.
POKE IT YOURSELF
aws route53 list-hosted-zones — list all hosted zones
aws route53 list-resource-record-sets --hosted-zone-id ZONE_ID — list all DNS records in a zone
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