# Why "Play Track 750,000" Is Instant and "Find Golden Hour" Isn't: Memory as Mailboxes

Find out why a music app plays track 750,000 in one step but has to search for a song by its title, and how a program keeps songs of different sizes without losing that one step.

![Cheat sheet: Why "Play Track 750,000" Is Instant and "Find Golden Hour" Isn't: Memory as Mailboxes](https://fsdtrainingmedia.blob.core.windows.net/public/images/2026/11/4674d7ada0e947c98d80c4ba1328b4a7.webp)

- Category: Data Structures
- Level: Novice
- Tags: Array (data-structures), data structures, Memory Address, Reference (software-development), software-development
- Updated: November 3, 2026

Source: https://www.ask-codey.com/cheat-sheets/ds-memory-as-mailboxes-cheat-sheet