The document that was 400 KB because of one field

A search document carrying the full product description as both an indexed text field and a stored copy, on a catalogue where descriptions run to several pages.

{
  "mappings": {
    "properties": {
      "description": {
        "type": "text",
        "index": true,
        "store": false
      },
      "description_html": {
        "type": "keyword",
        "index": false,
        "doc_values": false
      }
    }
  }
}

The rendered HTML was in the index so that search results could show it, which they never did — the results page fetches from the database anyway. Setting index: false and doc_values: false keeps the field retrievable from the source without any index structures, and the index went from 41 GB to 9. The better answer would have been not to store it at all.