The IronWorker doesn't seem to fulfill the same promise of simplicity that Lambda does. It's talking about scheduling and creating docker instances where Lambda says "just give us your code".
That said, you don't need to think about Docker if you don't want to and an IronWorker can be a few lines of code too, for example:
https://github.com/iron-io/dockerworker/blob/master/ruby/hel...
Or node: https://github.com/iron-io/dockerworker/blob/master/node/hel...