IT depend extremely on the application programming.
If only the threads (CPU power) is the issue increase the HW speed.
But often it is a mixture.
You should analyze why the threads are blocked, maybe increasing the DB connection might help.
Also the GC of the JVM might be a problem, in this case a split in deparate cluster instances are helpful.
So analyze it well, otherwise a optimization is a game of change
If you have special questions fell free to ask, your welcome.