Parse.Cloud.beforeSave( "Product", function( request, response ) {
    Parse.Cloud.useMasterKey();

    var objectToBeSaved = request.object;

    if ( objectToBeSaved.field == null ) {
        response.error( Error( "field cannot be empty!" ) ); // Save will not happen and the client will receive error
    } else {
        response.success( objectToBeSaved ); // Save will happen
    }
});

Parse.Cloud.define( "search", function( request, response ) {
    var pattern = request.params[ "body param name" ];

    var objectsQuery = new Parse.Query( "Product" );

    objectsQuery.find({
        success: function( objects ) {
            var filtered = objects.filter(function( obj ) {
                ....
            });

            response.success( filtered ); // Return the matched objects
        },
        error: function( err ) {
            response.error( err ); // Internal parse error
        }
    });
});