SELECT 
  cscart_products.* 
FROM 
  cscart_products 
WHERE 
  cscart_products.product_id IN (
    12546, 12633, 12573, 12548, 12580, 12576, 
    12565, 12567, 12549, 12581, 12557, 
    12558, 12570, 12578, 12568, 12547, 
    12569, 12584, 12592, 12575
  )

Query time 0.00064

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": 20,
      "filtered": 100,
      "index_condition": "cscart_products.product_id in (12546,12633,12573,12548,12580,12576,12565,12567,12549,12581,12557,12558,12570,12578,12568,12547,12569,12584,12592,12575)"
    }
  }
}