Insufficient shared_buffers limits PostgreSQL cache effectiveness

The default shared_buffers of 128 MB is too low for modern servers, causing PostgreSQL to constantly re-read data from disk instead of serving from cache. This degrades query performance, especially for read-heavy workloads.

Set shared_buffers to 25% of total RAM. This requires a PostgreSQL restart. Edit postgresql.conf and set shared_buffers = '4GB' (adjust based on your total RAM). Then restart PostgreSQL. Monitor cache hit ratio after the change.