This article explains how PostgreSQL manages data recovery through its Write-Ahead Logging (WAL) system. It covers the recovery lifecycle, including crash recovery, point-in-time recovery, and the role of WAL in maintaining data integrity during these processes.

The article discusses the implementation of checksums in SQLite's Write-Ahead Logging (WAL) mode, detailing how they ensure data integrity and consistency. It explores the algorithms used for the checksums and their impact on performance and reliability during database operations. Additionally, it highlights potential issues that can arise without proper checksum validation.

Postgres replication slots utilize two log sequence numbers (LSNs) — confirmed_flush_lsn and restart_lsn — to manage data streaming and retention effectively. The confirmed_flush_lsn indicates the last acknowledged data by the consumer, while the restart_lsn serves as a retention boundary for WAL segments needed for ongoing transactions. Understanding these differences is essential for troubleshooting replication issues and optimizing WAL retention in production environments.