How Do HashMaps Work Under the Hood? (putting together a toy implementation in Rust to understand performance optimization, collisions, and time complexities)

HashMaps are incredibly convenient, but treating them like a magical black box can make it easy to overlook where their performance comes from. In this article, I explain how HashMaps work using a simple implementation in Rust. I go through hash collisions and linear probing, why primary clustering hurts performance, load factors, resizing, and more. The implementation is intentionally simplified, but it gives a good picture of what's actually happening underneath a HashMap. Let me know your thoughts or any feedback you have! All writing, illustrations, and code are my own. AI was used to clean up wording and catch grammatical mistakes.