The copy is always a little behind

A news site. Six thousand article reads a second at peak, and about two hundred writes — a published edit, a comment, a view counter — all on one SQL database, which is out of headroom. Somebody suggests a second copy of it. What can that copy take off the first one?

• Both, evenly. Two databases means either one can take a read or a write, whichever has room.
• The reads. Every write still lands on one primary, and the copy answers with what it had a moment ago.
• Nothing until the rows are split by article id, because one box cannot hold the whole site twice.