1đź‘Ť
Your content is in a database. You aren’t required to work out the most efficient data structures to use to store the information; your database engine already does that. And it does it way better than you ever could. (That’s not a personal insult; databases store and retrieve information way better than ANYONE could.)
Ultimately, you do need to compare each of the 200 new numbers against each of the 1,000 numbers in your database. You don’t have to work out how to do that efficiently, though. Just ask the database if any of those numbers exist and it will (I guarantee) work out the most efficient possible way to do it.
For a database with many millions of records, the answer to the question “Does this value already exist?” should still come back in the tiniest fraction of a second.