How is the unique trace ID implemented? Vector clocks would be in use by your distributed data store for conflict resolution such as Riak does. Could you elaborate on how you've implemented such a system?
Imagine you have 3 services. A calls B calls C. A request goes into A. The request fails. Since there are 3 services involved, you want to be able to see the log statements of all 3 services, in order. To do this, you need a UUID that is passed from A to B to C and a vector clock that is incremented from A to B to C so you get perfect ordering. Passing the data around is not super hard (you can use HTTP headers, for example). The tricky bit is having a library that does the right thing in A and B and C. And if A is written in Java and B is written in NodeJS, that library better work on both!