Thank you for sharing this code @bjonen, it makes it much easier to test what’s going on, So what happens if that for each cell you have a very large number of queries to run (10000 I think), which is why it takes such a long time (on my laptop it took about one minute for the app to load). What you would like here I think is a gradient, that is a mapping between cell values and another property (background color): This would be only one simple operation per cell, so much faster. It is a feature that we’re interested in implementing here at plotly, but it’s likely that we’ll need to find first a sponsor interested in funding this development (https://plot.ly/products/consulting-and-oem/). So please stay tuned…