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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 (
    20541, 20542, 20543, 20544, 20545, 20546, 
    20547, 20548, 20549, 20550, 20551, 
    20552, 20553, 20554, 20555, 20556
  ) 
  AND cscart_product_review_prepared_data.storefront_id = 0

Query time 0.00892

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 (20541,20542,20543,20544,20545,20546,20547,20548,20549,20550,20551,20552,20553,20554,20555,20556)"
    }
  }
}