At a high level, what does DNS do, and what is Route 53's role in AWS?
What they are really testing: Whether you understand DNS as the name-to-address lookup layer and can place Route 53 as both a hosted DNS service and a routing tool. They also want awareness of TTL, because stale caches cause real outages during cutovers.
A real interview question
At a high level, what does DNS do, and what is Route 53's role in AWS?
What most people say
drag me
“DNS is the internet's phone book and Route 53 is just where AWS stores your domain.”
The phone book line is fine but it stops there. It misses that Route 53 is authoritative DNS with routing policies and health checks, and never mentions TTL, which is what bites people during a DNS-based failover or migration.
The follow-ups they ask next
You changed a record to point at a new server but half your users still hit the old one. Why?
Resolvers and clients cached the old record for its TTL, so they keep using it until the TTL expires. Lowering TTL before the change avoids this.
When would you use a weighted routing policy in Route 53?
To split traffic by percentage across endpoints, for example a canary or gradual rollout sending 10 percent to a new version, or balancing across two stacks.
What the interviewer is listening for
- Defines DNS as name-to-address resolution
- Knows Route 53 is authoritative DNS plus routing policies
- Brings up TTL and caching for cutovers
What sinks the answer
- Stops at the phone book analogy
- Unaware of routing policies or health checks
- No awareness of TTL or DNS caching
If you genuinely do not know
Say this instead of freezing. Reasoning out loud from what you do know beats silence every single time, and a good interviewer is listening for exactly that.
“DNS turns [a name into the address a client connects to] via records on [authoritative name servers]. Route 53 is [AWS's managed authoritative DNS] with [routing policies and health checks]. Changes are not instant because of [TTL caching], so before a cutover I [lower the TTL ahead of time].”
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