Altair builds on Vega-Lite but if you cannot do something in Vega-Lite, you can do it in Vega. Performance is a huge concern for us and we are working on some

Altair builds on Vega-Lite but if you cannot do something in Vega-Lite, you can do it in Vega. Performance is a huge concern for us and we are working on some improvements in that area. We will first focus on pushing computation and aggregation down into the Python kernel.