GUIDs, UUIDs and the Need for Unique Identifiers

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Summary: Globally Unique Identifiers (GUIDs) and Universally Unique Identifiers (UUIDs) provide a mechanism for uniquely identifying objects, records, and resources across systems without requiring a central authority.

Context

Almost every computer system needs a way to uniquely identify things.

  • Users
  • Documents
  • Orders
  • Projects
  • Devices
  • Events
  • Database records

What is a UUID?

UUID stands for: 

Universally Unique Identifier

A UUID is a 128-bit identifier designed to uniquely identify an object.

What is a GUID?

GUID stands for: 

Globally Unique Identifier

GUID is Microsoft's terminology for a UUID.

In modern systems, a Microsoft GUID is typically a UUID Version 4. 

GUID ≈ UUID v4

UUID Versions

UUID Version 4

Advantages:

  • Simple
  • Widely supported
  • Difficult to predict

Disadvantages:

  • Not time ordered
  • Can fragment indexes

UUID Version 7

Advantages:

  • Time ordered
  • Database friendly
  • Efficient indexing

Disadvantages:

  • Approximate creation times can be inferred

Conclusion

GUIDs and UUIDs solve the problem of uniquely identifying objects without central coordination.

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