SELECT 
  cscart_products.* 
FROM 
  cscart_products 
WHERE 
  cscart_products.product_id IN (
    12600, 12639, 15800, 12595, 12587, 12593, 
    12620, 12623, 12619, 12585, 12616, 
    12601, 12628, 12602, 12640, 12647
  )

Query time 0.00071

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 (12600,12639,15800,12595,12587,12593,12620,12623,12619,12585,12616,12601,12628,12602,12640,12647)"
    }
  }
}