POST /products/_search
{
  "query": {
    "function_score": {
      "query": {
        "match_all": {}
      },
      "script_score": {
        "script": {
          "source": "0.5 * log(sales + 1) + 0.5 * rating",
          "lang": "expression"
        }
      }
    }
  }
}