LRU Cache?

Short answer: Removes least recently used entries when full. public class LruCache<TKey,TValue>

Example code

{
private readonly int capacity;
private readonly Dictionary<TKey, LinkedListNode<(TKey,TValue)>> cache = new();
private readonly LinkedList<(TKey,TValue)> list = new();
public LruCache(int capacity) => this.capacity = capacity;
public TValue Get(TKey key)
{
if (!cache.ContainsKey(key)) return default;
var node = cache[key];
list.Remove(node);
list.AddFirst(node);
return node.Value.Item2;
}
public void Put(TKey key, TValue value)
{
if (cache.ContainsKey(key))
list.Remove(cache[key]);
if (cache.Count == capacity)
{
var last = list.Last; cache.Remove(last.Value.Item1); list.RemoveLast();
}
var newNode = new LinkedListNode<(TKey,TValue)>((key,value));
list.AddFirst(newNode);
cache[key] = newNode;
}
}

Real-world example (ShopNest)

Answer with: definition → one ShopNest-style story → trade-off → how you would verify it in production.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.