Agree with Tyler here.

I'd also do the following and move the `unless` statement for readability:

```ruby
def update_max_sizes
  unless @members.size == 0
    @max_bson_size = @members.map do |m|
      m.config['maxBsonObjectSize'] ?
        DEFAULT_MAX_BSON_SIZE : m.config['maxBsonObjectSize']}.min
    end

    @max_message_size = @members.map do |m|
      m.config['maxMessageSizeBytes'] ?
        DEFAULT_MAX_MESSAGE_SIZE : m.config['maxMessageSizeBytes']}.min
    end
  end
end
```