Using ag-grid with many rows and Autosave

I'm using ag-grid (javascript) to display a large amount of rows (about 3,000 or more) and allow the user to enter values and it should auto-save them as the user goes along. My current strategy is after detecting that a user makes a change to save the data for that row.

The problem I'm running into is detecting and getting the correct values after the user enters a value. The onCellKeyPress event doesn't get fired for Backaspace or Paste. However if I attach events directly to DOM fields to catch key presses, I don't know how to know what data the value is associated with. Can I use getDisplayedRowAtIndex or such to be able to reliably do this reliably? What is a good way to implement this?

EDIT: Additional detail

My current approach is to capture onCellEditingStopped and then getting the data from the event using event.data[event.column.colId]. Since I only get this event when the user moves to a different cell and not just if they finish typing I also handle the onCellKeyPress and get the data from event.event.target (since there is no event.data when handling this event). Here is where I run into a hard-to-reproduce problem that event.event.target is sometimes undefined.

I also looked at using forEachLeafNode method but it returns an error saying it isn't supported when using infinite row model. If I don't use infinite mode the load time is slow.

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