SELECT 
  product_id 
FROM 
  cscart_mb_ali_products 
WHERE 
  product_id IN (
    20957, 20958, 20959, 20960, 20961, 20962, 
    20963, 20964, 20965, 20966, 20967, 
    20968, 20969, 20970, 20971, 20972
  )

Query time 0.00013

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 (20957,20958,20959,20960,20961,20962,20963,20964,20965,20966,20967,20968,20969,20970,20971,20972)",
      "using_index": true
    }
  }
}