📣 Dash 1.5.0 released defers loading three things: Plotly.js (~3MB JS / ~900kB gzipped), XLSX (table export, ~1MB / ~300kB gzipped), the DataTable itself (~300kB JS / ~90KB gzipped). It also ensures that component resources are cached correctly.
At the moment other steps that can be taken are to (1) minimize other assets, (2) not import component libraries that are not used by the app.
In the coming releases more work will be done to defer loading additional components / dependencies and to improve caching of files in /assets.