Playbooks

Choose who owns the memory

An engine allocates memory for data it processes: leave it to the garbage collector, or take it off-heap as an arena, a typed pool, a dictionary or capped buffers? Four questions, then two checks on placement and peak.

Tune a buffer pool

A database caches disk pages in a buffer pool: isolate scans, use Clock, or pay for 2Q or ARC? Three questions pick the replacement policy; three checks find the pool's usable size and the failures upstream of the policy.

Ration memory across queries

Many queries share one machine's memory: list what cannot spill, check where grants come from, size grants in steps, decide between reservation and over-commit, and keep the pressure loop from oscillating.

Plan for running out of memory

When a query outgrows its memory, it spills to disk or is killed: list what cannot spill, compute what spilling really costs on your hardware, guard against one oversized key, and make sure a killed query retries with more memory.