Database
db={"collectionA":[{"someField":"123","anotherField":"456"},{"someField":"1234","anotherField":"4567"}],"collectionB":[{"someField":"123","otherField":"789"}]}
Query
db.collectionA.aggregate([{$lookup:{from:"collectionB",let:{some_field:"$someField"},pipeline:[{$match:{$expr:{$and:[{$eq:["$someField","$$some_field"]},{$eq:["$otherField","789"]}]}}}],as:"B"}},{$match:{$expr:{$gt:[{$size:"$B"},0]}}}])