UUID Best Practices for Database Design

Using UUIDs as primary keys offers many benefits, but requires careful implementation. Here are best practices to maximize performance and avoid common pitfalls.

1. Store as Binary, Not String

A UUID string takes 36 bytes, but the actual data is only 16 bytes. Store UUIDs as BINARY(16) or use your database's native UUID type to save 55% storage space and improve index performance.

-- PostgreSQL
CREATE TABLE users (
  id UUID PRIMARY KEY DEFAULT gen_random_uuid()
);

-- MySQL
CREATE TABLE users (
  id BINARY(16) PRIMARY KEY
);

2. Consider Time-Ordered UUIDs

Random UUIDs (v4) cause index fragmentation because new records are inserted at random positions. Consider using UUID v1, v6, or v7 for time-ordered identifiers that maintain better index locality.

3. Generate UUIDs in the Application

Generate UUIDs in your application code rather than the database. This allows you to know the ID before insertion, useful for creating related records or returning the ID immediately.

4. Use Consistent Formatting

Standardize on lowercase with hyphens for display, and binary for storage. Convert consistently at application boundaries to avoid comparison issues.

5. Index Considerations

• UUIDs work well as primary keys but increase index size
• Consider a separate auto-increment column for joins if performance is critical
• Use partial indexes when possible to reduce storage