Easy. You’re using SQLite in the catalog-remote package and SQLite is not thread-safe.
As in: You’ll run into problems as soon as you’re accessing the table in write-mode in parallel from two or more threads. For SQLite to work on a server, you need some kind of manager which pools the access attempts and processes them one at a time.
The reason for that is that SQLite is a flat-file format and writing to a file from two different sources at the same time is never a good idea.