DNS Resolution — Interactive Walkthrough
Companion to the "DNS Resolution" note in the Networking Math and Lookups series. Watch a lookup happen, try the cache yourself, and play with the TTL math.
1. Watch a lookup happen
Step through resolving www.example.com — notice how much of the work is the resolver making repeated round trips, not the client.
Scroll sideways to see the full chain on a narrow screen.
www.example.com.2. Try the cache yourself
Resolve a domain. The first time is a full lookup chain (like above); resolve it again before the TTL runs out and it's an instant cache hit. This demo uses a short 8-second TTL so you can actually watch it expire.
Cache lookup is a hash table: the domain name is hashed into a bucket so checking "do I already have this?" is O(1) regardless of how many domains are cached.
3. TTL math
How many actual queries reach the authoritative server, given a query rate and TTL, over some time window — matches the reasoning in the note.