What is SQL Server internal memory architecture (clerks, nodes, grants, and pressure signals)?

SQL Server memory is managed through memory clerks, grants, and internal/external pressure detection mechanisms.

SQL Server divides memory management into multiple layers. Memory clerks are components that track memory usage per subsystem (query execution, cache, buffer pool). Memory grants are allocations given to queries for operations like sorting and hashing. Memory nodes reflect NUMA topology, ensuring locality-aware allocation. SQL Server also monitors internal pressure (query demand) and external pressure (OS memory shortage). When pressure is detected, SQL Server trims caches, reduces grants, and may spill operations to tempdb.