Apex Interactive Debugger
The Apex Interactive Debugger is a feature available to those with either Performance or Unlimited edition organizations for free, or as a paid add-on for those using other editions. It is designed to operate in the same way as the Apex Replay Debugger, but in real time rather than on a debug log. Due to it being a paid feature, we are not able to cover it in detail.
At a high level, it operates in the same way as the Replay Debugger we just discussed, but in real time. That is, there is no need to retrieve a log file, as the debugger will stop at the correct breakpoints as you hit them within the code. This can be extremely useful as you are developing to step through the code. Should you have an interest in this tool, your Salesforce Account Executive can assist.
ISV Customer Debugger
If you have the Apex Interactive Debugger and operate as an (Independent Software Vendor) ISV, Salesforce allows you to log in to the sandboxes of your subscribers...