A much simpler solution is to keep your tables as they are (with an integer primary key), but add a non sequential public identifier too.

id => 123, public_id => 202cb962ac59075b964b07152d234b70

There are many ways to generate the public_id. A simple MD5 with a salt works quite well for extremely low effort.

Add a unique constraint on that column (which also indexes it), and you'll be safe and performant for hundreds of millions of rows!

Why do we developers like to overcomplicate things? ;)