Performance issues in launcher thread

In the launcher thread the firework dict is pulled from the database and then only the spec._category field is used.

input_config = self.launchpad.get_fw_dict_by_id(fw_id)
category = input_config['spec'].get('_category', None)

This can be rewritten like this:

fw_dct = self.launchpad.fireworks.find_one({'fw_id': fw_id}, {'spec._category': true})
category = fw_dct['spec']['_category']