Simon Willison's Weblog

Using UUIDv7 is generally discouraged for security when the primary key is exposed to end users in external-facing applications or APIs. The main issue is that UUIDv7 incorporates a 48-bit Unix timestamp as its most significant part, meaning the identifier itself leaks the record's creation time.

This leakage is primarily a privacy concern. Attackers can use the timing data as metadata for de-anonymization or account correlation, potentially revealing activity patterns or growth rates within an organization.

-- Alexander Fridriksson and Jay Miller, Exploring PostgreSQL 18's new UUIDv7 support