SELECT 
  cscart_products.* 
FROM 
  cscart_products 
WHERE 
  cscart_products.product_id IN (
    12591, 12582, 12590, 12571, 12632, 12559, 
    12631, 15938, 13091, 12551, 12638, 
    12634, 12636, 12635, 12599, 12627
  )

Query time 0.00082

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "table_name": "cscart_products",
      "access_type": "range",
      "possible_keys": ["PRIMARY"],
      "key": "PRIMARY",
      "key_length": "3",
      "used_key_parts": ["product_id"],
      "rows": 16,
      "filtered": 100,
      "index_condition": "cscart_products.product_id in (12591,12582,12590,12571,12632,12559,12631,15938,13091,12551,12638,12634,12636,12635,12599,12627)"
    }
  }
}