Without regular checkpoints, write-ahead logs would grow indefinitely and database startup recovery could take hours. However, flushing all dirty memory pages concurrently causes catastrophic storage queue saturation (Checkpoint Spikes). Modern production engines implement Spread Checkpoints: Flushing is distributed across time using checkpoint_completion_target = 0.9 to smooth I/O throughput across 90% of the checkpoint interval, eliminating latency spikes.
Internal Architecture Breakdown
Production Inspection Queries
PostgreSQL
SELECT checkpoints_timed, checkpoints_req, checkpoint_write_time, checkpoint_sync_time FROM pg_stat_bgwriter;
MySQL
SHOW GLOBAL STATUS LIKE 'Innodb_buffer_pool_pages_dirty';