Question 1

What is a UUID?

Accepted Answer

UUID (Universally Unique Identifier) is a 128-bit number used to uniquely identify information in computer systems. The standard format is 8-4-4-4-12 hexadecimal digits (e.g., 550e8400-e29b-41d4-a716-446655440000).

Question 2

What is the difference between UUID v4 and v7?

Accepted Answer

UUID v4 is purely random, with no meaningful structure. UUID v7 encodes a timestamp in the first 48 bits, making it sortable by time while maintaining uniqueness. UUID v7 is generally preferred for database primary keys because it improves index performance.

Question 3

Are generated UUIDs guaranteed to be unique?

Accepted Answer

While the probability of collision is astronomically low (1 in 2^122 for v4), it is not mathematically guaranteed. For practical purposes, UUIDs are considered unique enough for distributed systems without coordination.

Question 4

When should I use UUIDs?

Accepted Answer

Use UUIDs when you need unique identifiers across distributed systems, database primary keys, session tokens, API keys, or any scenario where centralized coordination for ID generation is impractical.

Feature	UUID v4	UUID v7
Structure	Fully random	Timestamp + random
Sortable	No	Yes (by time)
Database index	Poor (random inserts)	Good (sequential)
Use case	General uniqueness	Database keys, logs

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