SELECT 
  cscart_products.* 
FROM 
  cscart_products 
WHERE 
  cscart_products.product_id IN (
    12578, 12559, 12551, 12634, 12636, 12635, 
    12554, 12552, 12652, 12653, 12654, 
    12646, 12655, 12656
  )

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": 14,
      "filtered": 100,
      "index_condition": "cscart_products.product_id in (12578,12559,12551,12634,12636,12635,12554,12552,12652,12653,12654,12646,12655,12656)"
    }
  }
}