SELECT 
  product_id 
FROM 
  cscart_mb_ali_products 
WHERE 
  product_id IN (
    21695, 21696, 21697, 21698, 21699, 21700, 
    21701, 21702, 21703, 21704, 21705, 
    21706, 21707, 21708, 21709, 21710
  )

Query time 0.00015

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 (21695,21696,21697,21698,21699,21700,21701,21702,21703,21704,21705,21706,21707,21708,21709,21710)",
      "using_index": true
    }
  }
}