Build a DNS resolver with a TTL cache

Extend a resolver from direct records to alias chains, failures and time-limited cached answers.

Role: Research Engineer
Difficulty: Medium
Practice time: 90 min

The challenge

Build a resolver against a supplied record provider, starting with direct answers and extending it to alias chains, failures and cached responses. The provider simulates the network, so you can concentrate on resolution behaviour.

An alias may require several lookups before an answer is found, while a cached result has a limited lifetime. Extend the same resolver without losing the distinction between a valid answer, a missing name and a lookup error.

What you'll practise

Alias traversal
Follow the lookup chain while preserving the meaning of errors and responses.
Time-aware caching
Reuse results only while the applicable cached information remains valid.

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solution.pyPython 3.13

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Build a DNS resolver with a TTL cache

The challenge

What you'll practise

Alias traversal

Time-aware caching

Resolve paths with home expansion and symlinks

Build a weighted LRU cache

Implement an LRU cache

The challenge

What you'll practise

Alias traversal

Time-aware caching

Related challenges

Resolve paths with home expansion and symlinks

Build a weighted LRU cache

Implement an LRU cache