db={plans:[{planName:"TV1",planFeatures:{"AA1":true,"AA2":false,"AA3":true,"AA4":true,"AA5":false}},{planName:"TV2",planFeatures:{"AA1":true,"AA2":false,"AA3":false,"AA4":true,"AA5":false}}],planFeatures:[{key:"AA1",label:"ALPHA",},{key:"AA2",label:"BETA"}]}

db.planFeatures.aggregate([{$lookup:{from:"plans",let:{"kkey":"$key"},pipeline:[{$set:{"planFeatures5":{"$objectToArray":"$planFeatures"}}},{$match:{$expr:{$in:["$$kkey","$planFeatures5.k"]}}}],as:"paymentplans"}}])