# Why Does This Loop Take Seconds? Your Language's List

A loop over 100,000 orders takes seconds, and one call in it is why. Meet your language's list, the growing array under five names, and read its cost card before you pick a method.

![Cheat sheet: Why Does This Loop Take Seconds? Your Language's List](https://fsdtrainingmedia.blob.core.windows.net/public/images/2026/11/d03d3ab273e44e58b4ed95e78b356fad.webp)

- Category: Data Structures
- Level: Apprentice
- Tags: Array (javascript), ArrayList, data structures, Dynamic Array, List (python), List<T>
- Updated: November 3, 2026

Source: https://www.ask-codey.com/cheat-sheets/ds-built-in-lists-cheat-sheet