[{"appId":"1","targetFrom":"a","targetTo":"b"},{"appId":"2","targetFrom":"b","targetTo":"c"},{"appId":"3","targetFrom":"x","targetTo":"y"}]

db.collection.aggregate({$match:{$expr:{$and:[{appId:"1"},{$or:[{$in:["$targetFrom",["a","c"]]},{$in:["$targetTo",["a","c"]]}]}]}}})