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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 (
    21887, 21888, 21889, 21890, 21891, 21892, 
    21893, 21894, 21895, 21896, 21897, 
    21898, 21899, 21900, 21901, 21902
  ) 
  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 (21887,21888,21889,21890,21891,21892,21893,21894,21895,21896,21897,21898,21899,21900,21901,21902)"
    }
  }
}