Currently, the NodeJs Daemon queries the MySQL database for the new requests every 15 seconds. It will deal with one request at a time. In case the request takes longer than 15 seconds, and it might happen that more than 1 requests are being handled at the same time.
The jobs are handled asynchronously – non blocking. When a job is being processed, the MySQL table entries will be set to “in process” so that it will be be picked up twice by next run.