[{active:"true",time:"",unified_invitees:[{_id:1,milestone_status:[{milestone:"draft"},{milestone:"deleted"},]},{_id:2,milestone_status:[{milestone:"draft"},{milestone:"deleted"},]},{_id:3,milestone_status:[{milestone:"draft"},{milestone:"subscribed"},]},]}]

db.collection.aggregate([{$addFields:{unified_invitees:{$filter:{input:"$unified_invitees",as:"un",cond:{$anyElementTrue:{$map:{input:"$$un.milestone_status",as:"ms",in:{$eq:["$$ms.milestone","subscribed"]}}}}}}}}])