SELECT 
  product_id 
FROM 
  cscart_mb_ali_products 
WHERE 
  product_id IN (
    20925, 20926, 20927, 20928, 20929, 20930, 
    20931, 20932, 20933, 20934, 20935, 
    20936, 20937, 20938, 20939, 20940
  )

Query time 0.00014

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "table_name": "cscart_mb_ali_products",
      "access_type": "range",
      "possible_keys": ["product_id"],
      "key": "product_id",
      "key_length": "4",
      "used_key_parts": ["product_id"],
      "rows": 16,
      "filtered": 100,
      "attached_condition": "cscart_mb_ali_products.product_id in (20925,20926,20927,20928,20929,20930,20931,20932,20933,20934,20935,20936,20937,20938,20939,20940)",
      "using_index": true
    }
  }
}