FAQ and Gotchas

Are caches thread-safe by default?

No. Wrap a cache in a lock (Mutex, RwLock) or enable the concurrency feature to use built-in concurrent wrappers like ConcurrentClockRing.

Does get update policy metadata?

Yes. get updates recency or frequency depending on the policy. Use contains when you want to check presence without updating metadata.

What happens on insert at capacity?

The cache evicts an entry according to the selected policy.

Can I use zero capacity?

Policies handle zero capacity differently; some clamp to 1. Prefer explicit capacity >= 1 unless you are validating edge cases.

Why do some policies use Arc<V> internally?

Some policies store values behind Arc to minimize copies. The builder hides this detail so the unified Cache<K, V> API still works with owned values.