Majorly on my professional experience , tools technologies, latest technologies. Data structures , typical questions - Write your own Data structure implementation. Emphasis was on real-time support bugs/resolutions.Tools that will help the support/debug issues. My suggestion for the service engineer roles is to not get too carried away with data structures, algorithms ( these are necessary for the software developer role), instead concentrate on overall application , support, scenarios to debug large scale apps, tools and technologies, DevOp and Design.
