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Part 2: Relational Databases (RDBMS / PostgreSQL / MySQL) (6 - 25)

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Databases & System Design•Part 2: Relational Databases (RDBMS / PostgreSQL / MySQL) (6 - 25)

Write-Ahead Logging (WAL) and PITR:

In Simple Words: Before any change touches data files on disk, it is written to the append-only WAL. Point-In-Time Recovery (PITR): Allows replaying base backups plus archived WAL logs to restore a database to the exact second prior to an accidental DROP TABLE.

bash
# PostgreSQL PITR recovery configuration (postgresql.conf / recovery.signal):
restore_command = 'cp /mnt/wal_archive/%f %p'
recovery_target_time = '2026-11-06 14:32:00 UTC'
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MVCC and VACUUM in PostgreSQL: