S3QL is a lower level query language than relational SQL. For that reason, it takes more queries to retrieve all statement associated with a certain number of Items. To avoid the wait time usually associated with waiting for one query to finish before starting the next, there are several options in PHP and other languages to run the queries in parallel.
For example, if using PHP you can use this small function to achieve that goal. Once the function 'goparallel' is included in your script, use the following syntax to perform your queries in parallel and save the result in a single "results" array: