How to Query Historical Row States in PostgreSQL Using SCD Type 4

Tracking how database records looked at a specific point in the past is a common challenge when data gets updated over time. Several modeling approaches exist, including event sourcing, in-place versioning (SCD Type 2), periodic snapshotting, and the SCD Type 4 pattern. SCD Type 4 solves the problem by maintaining a separate history table that mirrors the main table, with valid_from and valid_to timestamps to track each version of a record. A row-level trigger automatically writes every insert, update, and delete into the history table, keeping the application code free from dual-write logic. This allows developers to reconstruct the exact state of any record at an arbitrary past timestamp using a single SELECT query.