SELECT 
  cscart_products.* 
FROM 
  cscart_products 
WHERE 
  cscart_products.product_id IN (
    12643, 12649, 12609, 12644, 12650, 12652, 
    12653, 12654, 12646, 12655, 12656, 
    12645, 12651, 12597, 12615, 12603, 
    12629, 12604
  )

Query time 0.00051

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": 18,
      "filtered": 100,
      "index_condition": "cscart_products.product_id in (12643,12649,12609,12644,12650,12652,12653,12654,12646,12655,12656,12645,12651,12597,12615,12603,12629,12604)"
    }
  }
}