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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 (
    21455, 21456, 21457, 21458, 21459, 21460, 
    21461, 21462, 21463, 21464, 21465, 
    21466, 21467, 21468, 21469, 21470
  ) 
  AND cscart_product_review_prepared_data.storefront_id = 0

Query time 0.00019

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 (21455,21456,21457,21458,21459,21460,21461,21462,21463,21464,21465,21466,21467,21468,21469,21470)"
    }
  }
}