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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 (
    20605, 20606, 20607, 20608, 20609, 20610, 
    20611, 20612, 20613, 20614, 20615, 
    20616, 20617, 20618, 20619, 20620
  ) 
  AND cscart_product_review_prepared_data.storefront_id = 0

Query time 0.00014

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 (20605,20606,20607,20608,20609,20610,20611,20612,20613,20614,20615,20616,20617,20618,20619,20620)"
    }
  }
}