It looks like my interest is flagging. Week three is all about handling exceptions, latencies, asynchronous computation, and related issues within the programming language rather than as an add-on. If you know how Option works in Scala, this is very similar. The general idea is to wrap a computational result in something that reflects the possibility that it may fail, or not happen on time, etc. To do that they invented a large number of wrappers (Future, Promise, Try, ... ) and many methods to deal with them. I'm not that interested in the details of how that works. So I'm not spending much effort on this material. It should be of interest to people who want to work at the level of server implementation and synchronous communication among distributed processes. The assignment is called nodeScala. It implements a web server, presumably similarly to how NodeJS implements a server. If you want to work in this area, you should look at this material. It's probably the most complete implementation of a server in that it deals with all sorts of failures and time-outs as first class elements of the language -- in much the same way as Scala allows functions to be first class elements of the language.