What skills make you a more resourceful and *productive* developer to a fast-paced trading system? These usually have little to do with arch design. Almost never asked in interviews, ironically.
See also my post on 2 types of tools.
1) IDE remote debugging
** breakpoint on exception
** conditional breakpoint
** compile with local vars
2) IDE refactor — rename, search
) reflection, dynamic proxy
) jconsole, JMX
) requesting Runtime.gc()
) generics for algorithm abstraction but this tends to be too complex
) code gen? cache triggers
Threading? nope it seldom adds too much biz value