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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 (
    20685, 20686, 20687, 20688, 20689, 20690, 
    20691, 20692, 20693, 20694, 20695, 
    20696, 20697, 20698, 20699, 20700
  ) 
  AND cscart_product_review_prepared_data.storefront_id = 0

Query time 0.00023

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 (20685,20686,20687,20688,20689,20690,20691,20692,20693,20694,20695,20696,20697,20698,20699,20700)"
    }
  }
}