Why Modern Hash Tables Dropped Linked Lists for Cache-Friendly Designs

Introductory computer science courses teach hash tables using linked-list separate chaining, but modern production runtimes like Rust, Python, and Go have largely abandoned this approach. The core reason is hardware physics: random heap pointer traversal causes repeated CPU cache misses, stalling processors for hundreds of clock cycles while data is fetched from slow DRAM. Modern hash tables instead use open addressing, storing all key-value pairs in a single contiguous array so that probing adjacent slots reuses data already loaded into fast L1 cache lines. However, naive open addressing introduces its own problems, including primary clustering and the need for deletion tombstones that degrade lookup performance. Advanced techniques such as Swiss Tables and Robin Hood Hashing were developed to address these flaws while preserving cache efficiency.