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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 (
    21743, 21744, 21745, 21746, 21747, 21748, 
    21749, 21750, 21751, 21752, 21753, 
    21754, 21755, 21756, 21757, 21758
  ) 
  AND cscart_product_review_prepared_data.storefront_id = 0

Query time 0.00031

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 (21743,21744,21745,21746,21747,21748,21749,21750,21751,21752,21753,21754,21755,21756,21757,21758)"
    }
  }
}