isStaleFor (accessMode) {
    return (
      this.expirationTime.lessThan(Date.now()) ||
      this.routers.length < MIN_ROUTERS ||
      (accessMode === READ && this.readers.length === 0) ||
      (accessMode === WRITE && this.writers.length === 0)
    )
  }
Check if this routing table is fresh to perform the required operation.
@param {string} accessMode the type of operation. Allowed values are {@link READ} and {@link WRITE}.
@return {boolean} `true` when this table contains servers to serve the required operation, `false` otherwise.