UUID vs Auto-Increment IDs: Pros and Cons
Choosing between UUIDs and auto-incrementing integers for primary keys is a fundamental database design decision. Let's compare both approaches.
Auto-Increment Integers
Pros
- Small storage (4-8 bytes vs 16 for UUID)
- Better index performance
- Human-readable and easy to debug
- Natural ordering by creation time
Cons
- Requires database coordination
- Can't generate offline
- Reveals record count and creation order
- Merge conflicts in distributed systems
UUIDs
Pros
- Generate anywhere without coordination
- Perfect for distributed systems
- Impossible to guess
- No conflicts when merging data
Cons
- Larger storage requirement (16 bytes)
- Index fragmentation (v4)
- Not human-friendly
- Slightly slower joins
When to Choose What
Choose Auto-Increment
- Single database instance
- Performance is critical
- Storage is limited
- Internal-only IDs
Choose UUIDs
- Distributed systems
- Offline-first apps
- Public-facing IDs
- Data from multiple sources
The Hybrid Approach
Many applications use both: auto-increment for internal references and joins, UUIDs for external/public identifiers. This gives you the performance benefits of integers with the security of UUIDs for public APIs.
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