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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 (
    20765, 20766, 20767, 20768, 20769, 20770, 
    20771, 20772, 20773, 20774, 20775, 
    20776, 20777, 20778, 20779, 20780
  ) 
  AND cscart_product_review_prepared_data.storefront_id = 0

Query time 0.00016

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 (20765,20766,20767,20768,20769,20770,20771,20772,20773,20774,20775,20776,20777,20778,20779,20780)"
    }
  }
}