Maxim Mironjuk
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January 21, 2026
Once a project moves from auto-increment primary keys to globally unique IDs, the choice often falls on UUIDv4, simply because it is the most familiar standard. What frequently gets overlooked is that a fully random ID fragments B-tree indexes in a way auto-increment keys never would, and that can cost noticeable performance on large, fast growing tables. The Symfony UID component offers UUID and ULID under one consistent API, and this article shows exactly when each format is genuinely the better choice and how both integrate cleanly with Doctrine.