Support requesting acknowledgement that a write operation has propagated to a specified number of tagged nodes, without requiring users to define a custom write concern in the replica set config. Accept a write concern with the custom write concern specification embedded in the w option:

db.collection.insertOne(
   { id: "xyz", status: "A" },
   { writeConcern: { w: { "dc_va": 2, "dc_ca": 1 } } }
)