[{"_id":{"$oid":"5ec8f74f32973c7b7cb7cce9"},"createdAt":{"$date":"2020-05-23T10:13:35.012Z"},"updatedAt":ISODate("2020-02-20T13:37:09.861Z")},{"_id":{"$oid":"5ec8ef8a2b6e5f78fa20443c"},"createdAt":{"$date":"2020-05-23T09:40:26.089Z"},"updatedAt":{"$date":"2020-07-23T07:54:01.833Z"}},{"_id":{"$oid":"5ed5e1a3962a3960ad85a1a2"},"createdAt":{"$date":"2020-06-02T05:20:35.090Z"},"updatedAt":{"$date":"2020-07-29T14:02:52.295Z"}},{"_id":{"$oid":"5ed629ec6d87382c608645d9"},"createdAt":{"$date":"2020-06-02T10:29:00.204Z"},"updatedAt":{"$date":"2020-06-02T10:29:00.204Z"}}]

db.collection.aggregate([{$facet:{new_users:[{$match:{createdAt:{$gte:ISODate("2020-08-01")}}},{$group:{_id:{$dateToString:{format:"%Y-%m",date:"$createdAt"}},new_users:{$sum:1}}}],active_users:[{$match:{$expr:{$gte:["$updatedAt",{$subtract:["$$NOW",1.577e+10]}]}}},{$group:{_id:{$dateToString:{format:"%Y-%m",date:"$updatedAt"}},active_users:{$sum:1}}}]}},{$project:{root:{$concatArrays:["$new_users","$active_users"]}}},{$unwind:"$root"},{$group:{_id:"$root._id",new_users:{$sum:"$root.new_users"},active_users:{$sum:"$root.active_users"}}}])