2026-06-04 · 5 min read
- uuid
- backend
Universally Unique Identifiers (UUIDs) are 128-bit values, usually shown as 36-character strings. Version 4 UUIDs are random and ideal for database primary keys, correlation IDs in logs, and idempotency keys.
UUID v4 vs other versions
For most web apps, v4 is the safe default when ordering is not required.
- v4 — random, no coordination needed
- v1 — time-based, can leak MAC-derived data (avoid in public IDs)
- v7 — time-ordered random (growing adoption for databases)
Correlation IDs
Attach a UUID to each inbound HTTP request and propagate it through microservices. Log the same ID everywhere to stitch traces in Kibana or CloudWatch without guessing.
Collision probability
Random UUID collisions are astronomically unlikely for practical deployments. Still use database unique constraints as the source of truth.