[{"_id":1234,"Processes":[{"0_0":"aaaa","0_1":"bbbb"},{"1_0":"cccc","1_1":"dddd"},{"2_0":"eeee","2_1":"ffff"},]},{"_id":5678,"processes":[{"0_0":"gggg","0_1":"hhhh"},{"1_0":"iiii","1_1":"jjjj"},{"2_0":"kkkk","2_1":"mmmm"},]}]

db.collection.aggregate([{"$unwind":"$processes"},{"$replaceRoot":{"newRoot":{"$mergeObjects":[{"_id":"$_id"},"$processes"]}}}])