Request Timeout: Server was too busy to process this request

The server was not busy. A query waited for a row lock, and MariaDB stopped it after 50 seconds with error 1205, Lock wait timeout exceeded. Another transaction held that lock. This is a bug in the application, not a limit of the plan.

Find the cause

1. Do the action a second time. While it runs, open the process list of your site. The list shows the query that waits and the query that blocks it.
2. If the process list is empty, read the slow queries of your site.
3. Search the Error Log for QueryTimeoutError. The traceback names the code that failed.

A new controller hook or scheduled job is the usual cause.

Correct it

• Keep transactions short. Do the slow work first, then write to the database.
• Update rows in batches. Commit after each batch.
• If two jobs write to the same document, run them one after the other.