save only recent 30 post meta fileds in wordpress post

Hi, I hope you're all well, I want a script that fetches youtube video ids and save in my WordPress post meta fields, but it has a problem they save lot of meta fields.. but i want to save just recently fetched only 30 meta fields, example I have complete have 30 fileds and script run again and fetch 2 more ids then script delete last 2 fileds and add recent 2 fileds...