Buffer Pools, Caches, and the Memory Hierarchy

This article is Part 7 of a 10-part series on query engine design, focusing on memory management in database systems. It covers the memory hierarchy's exponential latency gaps between CPU cache, RAM, SSD, and HDD, and explains how caching strategies are crucial for performance. The article details buffer pools used in OLTP databases like PostgreSQL and MySQL, including page replacement policies such as LRU and Clock. It also discusses columnar and result caches for OLAP approaches, memory budget tradeoffs, and spill-to-disk strategies. Aimed at IT and technology professionals, it provides technical insights into database engineering and memory optimization.