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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 (
    21567, 21568, 21569, 21570, 21571, 21572, 
    21573, 21574, 21575, 21576, 21577, 
    21578, 21579, 21580, 21581, 21582
  ) 
  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 (21567,21568,21569,21570,21571,21572,21573,21574,21575,21576,21577,21578,21579,21580,21581,21582)"
    }
  }
}