Episode Details

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Learn how PostgreSQL double buffering wastes RAM, increases latency, and hurts query performance — plus the 25% shared_buffers rule to fix it.
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Many PostgreSQL performance issues aren’t caused by too little RAM, but by allocating memory to the wrong layer. Postgres and the OS both cache the same data independently, creating a “double buffering” problem that wastes memory and increases latency. This guide explains how shared_buffers and the OS page cache interact, why the 25% shared_buffers rule matters, how to diagnose cache pressure with pg_buffercache, and when tuning stops helping because the dataset itself has outgrown memory.