@Override
  public PropertySource load() {
    Map<String, Object> ratelimiterProperties = new HashMap<String, Object>();
    Map<String, String> envs = getEnv();
    for (Map.Entry<String, String> env : envs.entrySet()) {
      if (env.getKey().startsWith(PropertyConstants.PROPERTY_KEY_PREFIX)) {
        ratelimiterProperties.put(env.getKey(), env.getValue());
      }
    }
    PropertySource source = new PropertySource();
    source.addProperties(ratelimiterProperties);
    return source;
  }
This class loads environment configuration from system environment variables.
src/main/java/com/eudemon/ratelimiter/env/loader/SystemPropertySourceLoader.java