SELECT 
  * 
FROM 
  cscart_sg_ew_warranty_mapping 
WHERE 
  product_id = 429455 
  AND status = 'A' 
ORDER BY 
  FIELD(mapping_type, 'manual', 'auto') ASC

Query time 0.00017

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost": 0.00345856,
    "nested_loop": [
      {
        "read_sorted_file": {
          "filesort": {
            "sort_key": "field(cscart_sg_ew_warranty_mapping.mapping_type,'manual','auto')",
            "table": {
              "table_name": "cscart_sg_ew_warranty_mapping",
              "access_type": "ref",
              "possible_keys": ["product_plan"],
              "key": "product_plan",
              "key_length": "4",
              "used_key_parts": ["product_id"],
              "ref": ["const"],
              "loops": 1,
              "rows": 1,
              "cost": 0.00345856,
              "filtered": 100,
              "attached_condition": "cscart_sg_ew_warranty_mapping.product_id <=> 429455 and cscart_sg_ew_warranty_mapping.`status` = 'A'"
            }
          }
        }
      }
    ]
  }
}