SELECT 
  cscart_product_review_prepared_data.product_id AS product_id, 
  cscart_product_review_prepared_data.average_rating AS average_rating, 
  cscart_product_review_prepared_data.reviews_count AS reviews_count 
FROM 
  cscart_product_review_prepared_data 
WHERE 
  cscart_product_review_prepared_data.product_id IN (
    391745, 389240, 389011, 389261, 389441, 
    389260, 389010, 415702, 389415, 389401, 
    389262, 389440, 389393, 415642, 389239, 
    389394
  ) 
  AND cscart_product_review_prepared_data.storefront_id = 0

Query time 0.00036

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "5.87"
    },
    "table": {
      "table_name": "cscart_product_review_prepared_data",
      "access_type": "ALL",
      "possible_keys": [
        "PRIMARY"
      ],
      "rows_examined_per_scan": 19,
      "rows_produced_per_join": 16,
      "filtered": "84.21",
      "cost_info": {
        "read_cost": "2.67",
        "eval_cost": "3.20",
        "prefix_cost": "5.87",
        "data_read_per_join": "256"
      },
      "used_columns": [
        "product_id",
        "storefront_id",
        "average_rating",
        "reviews_count"
      ],
      "attached_condition": "((`webmarco`.`cscart_product_review_prepared_data`.`storefront_id` = 0) and (`webmarco`.`cscart_product_review_prepared_data`.`product_id` in (391745,389240,389011,389261,389441,389260,389010,415702,389415,389401,389262,389440,389393,415642,389239,389394)))"
    }
  }
}