What is SQL Server internal memory pressure detection and eviction policy?

SQL Server detects memory pressure and evicts cache entries using LRU-like and cost-based algorithms.

SQL Server monitors internal and external memory pressure signals. Under pressure, it reduces buffer pool usage, evicts least recently used pages, and trims caches like plan cache and columnstore segments. Eviction is not purely LRU; it also considers page hotness and cost. Severe pressure may lead to query memory grants being reduced, increasing spills.