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 (
    4, 1, 5, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 
    17, 18, 19
  ) 
  AND cscart_product_review_prepared_data.storefront_id = 0

Query time 0.00038

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "table_name": "cscart_product_review_prepared_data",
      "access_type": "ALL",
      "possible_keys": ["PRIMARY"],
      "rows": 52,
      "filtered": 30.76922989,
      "attached_condition": "cscart_product_review_prepared_data.storefront_id = 0 and cscart_product_review_prepared_data.product_id in (4,1,5,7,8,9,10,11,12,13,14,15,16,17,18,19)"
    }
  }
}

Result

product_id average_rating reviews_count
5 3.67 3
1 4.00 3
8 4.00 1