UUID vs Sequential IDs: Which Should You Use in Your Database?

Primary key strategy is one of the most consequential database design decisions you make. It affects query performance, storage requirements, URL security, and distributed system scalability. Understanding the trade-offs clearly helps you make the right choice for each context.

Sequential IDs: Strengths and Weaknesses

Auto-increment integers (1, 2, 3...) are compact (4 or 8 bytes vs 16 for UUID), human-readable, naturally ordered, and fast to index. The weakness is information leakage: /orders/1 exposes your order volume; /users/42 confirms the 41 users that exist. Sequential IDs also require coordination in distributed systems — two nodes generating IDs independently will collide.

UUID v4: Strengths and Weaknesses

A UUID v4 is a 128-bit random identifier: 550e8400-e29b-41d4-a716-446655440000. It carries no sequential information, cannot be guessed or enumerated, and any system can generate one without coordination. The collision probability — approximately 1 in 5.3 × 10³⁶ — is effectively impossible in practice. The cost is size (16 bytes vs 4), random insertion order causing B-tree page splits, and reduced readability in logs.

When Each Is the Right Choice

Use UUID v4 for distributed systems, public-facing IDs in URLs and APIs, and identifiers generated before database insertion (for optimistic UI or event sourcing). Use sequential IDs for single-database internal systems where IDs are never exposed publicly and insertion performance is critical. Generate batches of UUIDs for seed scripts and test fixtures using the UUID Generator — up to 100 at once, copied with one click.