A backdoor requires malicious intent, otherwise it’s just a vulnerability

The exploit requires physical access. It’s not exploitable in 99% of cases

But is it fast?

Linux has good security, simply chmod the seats on the left so the wolves don’t get execute permissions

PostgreSQL can even run WebAssembly (with an extension)

Every major SQL database supports json manipulation nowadays. I know MariaDB and MySQL and SQLite at least support it natively.

It’s entirely possible to sort and filter inside JSON data in most SQL dialects. You can even add indexes.