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DNS

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Every request starts with a lookup

DNS translates a hostname into an address or another name. It is a hierarchical, aggressively cached, globally distributed database, and it sits in front of the connections users make to your service.

On a cache miss, a recursive resolver walks the tree: a root server points it at the nameserver for .com, which points it at the nameserver for your domain, which finally answers. Each step costs network work, but clients and resolvers cache answers, so most application lookups stop much earlier.

That caching is what makes DNS fast. It is also what makes DNS changes slow, and the two facts are the same fact.

browser cache
   └─ OS cache
       └─ resolver (ISP) cache
           └─ root  →  .com  →  your nameserver

A cache hit anywhere short-circuits the rest.
Most lookups never leave the resolver.
Back: Performance vs Scalability

3 components2 connections0:00

Traffic
4Kreq/s
p50
45ms
p99
101ms
Errors
0.06%
Dropped
2.4req/s
Cost
$534/mo