[{"_id":1,"title":"dummy title","assignments":[{"_id":1,"name":"a1","members":[{"_id":11,"full_name":"john doe","aga":18},{"_id":12,"full_name":"john doe2","aga":18}]}],"settings":[{"type":"light","status":"enabled"},{"type":"flare","status":"disabled"},{"type":"toolbar","status":"enabled"}]}]

db.collection.aggregate([{$project:{title:1,"memberids":"$assignments.members._id",/**"assignments._id": true,*"assignments.name": true,*/active_settings:{$reduce:{input:"$settings",initialValue:[],in:{$cond:[{$eq:["$$this.status","enabled"]},{$setUnion:["$$value",["$$this.type"]]},"$$value"]}}}}}])