Long story short, you’re holding multiple transactions open. That’s a lot of bookkeeping overhead if there’s a lot of changes. A system with a few million rows

Long story short, you’re holding multiple transactions open. That’s a lot of bookkeeping overhead if there’s a lot of changes. A system with a few million rows and moderate load on a reasonably-sized server for that load will slam to a halt. Then come the “site is down and the world is ending” tickets, messages, emails, and phone calls.