Stop using UUID v4 as your database primary key

I spent a while wondering why inserts on a particular table were getting slower as it grew. The table had a UUID v4 primary key and a few indexes. The data wasn't huge - a few million rows - but write performance was noticeably degrading. The problem wasn't the query. It was the UUID. What's actually happening UUID v4 is random by design. Every new ID lands at a completely unpredictable position in the B-tree index. So every insert causes the database to find that random position, potentially sp