private Optional<String> getSystemDefaultStreamProperty(String systemName, String propertyName) {
    Map<String, String> defaultStreamProperties = getDefaultStreamProperties(systemName);
    String defaultStreamProperty = defaultStreamProperties.get(propertyName);
    if (StringUtils.isNotEmpty(defaultStreamProperty)) {
      return Optional.of(defaultStreamProperty);
    } else {
      String fallbackStreamProperty = get(String.format(SYSTEM_ID_PREFIX, systemName) + propertyName);
      if (StringUtils.isNotEmpty(fallbackStreamProperty)) {
        return Optional.of(fallbackStreamProperty);
      } else {
        return Optional.empty();
      }
    }
  }
Gets the system-wide default for the {@code propertyName} for the {@code systemName}.
This will check in a couple of different config locations for the value.
samza-core/src/main/java/org/apache/samza/config/SystemConfig.java