This is a smart solution to the problem, if you must use OFFSET. That said, if you can avoid OFFSET, do, as it's typically considerably slower than a simple indexed range query.

If you're OFFSET-ing, say, 1000 records, I believe the database needs to load those 1000 records in some way, to exclude them from the result set (it's possible mysql does this differently than postgres). With a ranged query and a cursor (e.g. select * from tweets where created_at > CURSOR LIMIT 20) is, generally, more efficient. But cursored range queries don't make sense in a lot of cases and often come with some additional complexity in the code.