The free tier does require registration and use of an API license key with each data workload, so you will need to register for a free Interzoid account with an email address to obtain access if you have not already.
The free tier allows up to 1000 record/row data workloads processed without credit usage required for either database table rows or CSV file rows. For table or file record counts higher than 1000 records, the first 1000 records are free as well.
For example, 600 and 800 record data workloads are free, whereas a 2500 record data workload (CSV file or database table) will use 1500 credits. A 5000 record workload will use 4000 credits, and so on.