Interactive layered sankey (total of 28k nodes via AJAX)

I have 28,000 nodes I want to plot on a sankey. Obviously I can't visualize this all at once so I need to show it in pieces; showing two layers at a time. Each time someone clicks a new path/layer on the right the sankey should then drill down and load the next set of info via AJAX. The clicked node is then on the left with all paths from it going to the right. I guess there should also be a button somewhere to go back 'upwards' on the path, also. Viz library preferences are D3 and Highcharts.