presto-resource-group-managers/src/main/java/io/prestosql/plugin/resourcegroups/db/DbResourceGroupConfigurationManager.java/DbResourceGroupConfigurationManager/getCpuQuotaPeriodFromDb
class DbResourceGroupConfigurationManager:    private synchronized Optional<Duration> getCpuQuotaPeriodFromDb()
    {
        List<ResourceGroupGlobalProperties> globalProperties = dao.getResourceGroupGlobalProperties();
        checkState(globalProperties.size() <= 1, "There is more than one cpu_quota_period");
        return (!globalProperties.isEmpty()) ? globalProperties.get(0).getCpuQuotaPeriod() : Optional.empty();
    }