Postgres itself has no issue with 1000 simple requests per second. On normal notebook hardware you'll get easily several thousand requests per second if you're just looking up small amounts of data by the primary key. And that is without any optimization and with non-DB overhead included. The actual performance you can get is probably quite a bit higher, but I've seen ~4-6k requests per second on naive, unoptimized endpoints that just look up some data in Postgres.