class ConfigGetParameterHandler {

  public Set<String> getKeysByPrefix(String prefix) {
    if (prefix == null) {
      prefix = "";
    }

    TreeSet<String> keysWithPrefix = new TreeSet<>();

    ConfigContainer activatedConfigs = getConfigsFromCache(activatedConfigsCache);
    if (activatedConfigs != null) {
      keysWithPrefix.addAll(getKeysByPrefix(prefix, activatedConfigs));
    }

    ConfigContainer defaultsConfigs = getConfigsFromCache(defaultConfigsCache);
    if (defaultsConfigs != null) {
      keysWithPrefix.addAll(getKeysByPrefix(prefix, defaultsConfigs));
    }

    return keysWithPrefix;
  }

  public  ConfigGetParameterHandler(
      ConfigCacheClient activatedConfigsCache, ConfigCacheClient defaultConfigsCache);

}