code: public Duration getNextRetryInterval(String clientId, Exception lastException, Duration remainingTime) {
          int baseWaitTime = 0;
          synchronized (this.serverBusySync) {
              if (lastException != null
                      && (lastException instanceof ServerBusyException || (lastException.getCause() != null && lastException.getCause() instanceof ServerBusyException))) {
                  baseWaitTime += ClientConstants.SERVER_BUSY_BASE_SLEEP_TIME_IN_SECS;
              }
          }
  
          return this.onGetNextRetryInterval(clientId, lastException, remainingTime, baseWaitTime);
      }
docs: Gets the Interval after which nextRetry should be done.
  
  @param clientId      clientId
  @param lastException lastException
  @param remainingTime remainingTime to retry
  @return returns 'null' Duration when not Allowed