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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 (
    21407, 21408, 21409, 21410, 21411, 21412, 
    21413, 21414, 21415, 21416, 21417, 
    21418, 21419, 21420, 21421, 21422
  ) 
  AND cscart_product_review_prepared_data.storefront_id = 0

Query time 0.00015

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "table_name": "cscart_product_review_prepared_data",
      "access_type": "ALL",
      "possible_keys": ["PRIMARY"],
      "rows": 5,
      "filtered": 100,
      "attached_condition": "cscart_product_review_prepared_data.storefront_id = 0 and cscart_product_review_prepared_data.product_id in (21407,21408,21409,21410,21411,21412,21413,21414,21415,21416,21417,21418,21419,21420,21421,21422)"
    }
  }
}