def METHOD_NAME(app_configs, **kwargs):
    allowed_keys = {'PROXY_FOR_STANDBYS', 'PROXY', 'SHARDS', 'PLPROXY_HOST'}
    messages = []
    for db, config in settings.DATABASES.items():
        if 'PLPROXY' in config:
            unknown_keys = set(config['PLPROXY']) - allowed_keys
            if unknown_keys:
                messages.append(checks.Warning(
                    f'Unrecognised PLPROXY settings: {unknown_keys}'
                ))
    try:
        from corehq.sql_db.config import plproxy_config, _get_standby_plproxy_config
        if plproxy_config:
            _get_standby_plproxy_config(plproxy_config)
    except PartitionValidationError as e:
        messages.append(checks.Error(f'Error in PLPROXY standby configuration: {e}'))
    return messages