[eatonphil]

Try finding an entry in a list of 100 elements. Then try finding an entry in a list of 10 million elements.

Then make a hash table out of the list and try finding an entry in the hash table of 100 elements and the hash table of 10 million elements.

If you want to take it further, try building an in-memory database. Benchmark how it works with and without indexes as the number of items in the database grows.