Performance Lab

Clustered Index Insert Cost

Relative I/O cost of inserting 1M rows into a B-Tree index. Lower is better.

Why?Random v4 UUIDs cause "Page Splitting". Instead of appending to the end of the index (like v7 or Integer), the database has to rewrite middle pages constantly.

The Birthday Paradox

Probability of at least one collision vs. Number of UUIDs generated.

Takeaway: You need to generate 100 Quintillion UUIDs to reach even a 1% chance of collision. It is effectively impossible in human terms.