[{"lastImageUrl":"s3://dplus-bucket-eu/folder1/folder2/img.png"},]

db.collection.update({},[{$set:{lastImageUrl:{$reduce:{input:{$map:{input:{$split:["$lastImageUrl","/"]},in:{$cond:[{$eq:["$$this","/kidplus-bucket-eu"]},"kidplus-bucket-demo","$$this"]}}},initialValue:"","in":{"$cond":{"if":{"$eq":["$$value",""]},"then":"$$this","else":{"$concat":["$$value","/","$$this"]}}}}}}}])