SELECT 
  COUNT(*) 
FROM 
  cscart_orders 
WHERE 
  company_id = 19 
  AND status = 'C' 
  AND is_parent_order = 'N'

Query time 0.00068

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "table_name": "cscart_orders",
      "access_type": "ref",
      "possible_keys": ["status", "company_id"],
      "key": "company_id",
      "key_length": "4",
      "used_key_parts": ["company_id"],
      "ref": ["const"],
      "rows": 1,
      "filtered": 39.91228104,
      "attached_condition": "cscart_orders.`status` = 'C' and cscart_orders.is_parent_order = 'N'"
    }
  }
}