Node.js/V8 settings for Heroku web

[Jarka]

Hello,

How many of you use "custom" settings for the Heroku web instances ? As you know the Heroku has limited the dyno size to 512MB which could go over but then alert is thrown. 

With the default V8 settings the memory limit is in 1.4Gb which allows to grow the application heap and memory usage quite high without the GC cleanup. So should the V8 option 

--max-old-space-size be set to lets say 512 or 600, are there any other ? 

Also is there any use of `cluster` module or it doesn't have any difference, because there is only one core to use ?

Thank you!