I mean, setting up Zookeeper, tweaking the kernel settings, configuring the hardware, the kind of stuff mentioned in guides like https://medium.com/@ankurrana/things-nobody-will-tell-you-se... and https://dungeonengineering.com/the-kafkaesque-nightmare-of-m.... Apparently you can do without Zookeeper now, but that's another choice to make, possibly doing careful experiments with both choices to see what's better. Much more discussion in https://news.ycombinator.com/item?id=37036291.
None of this applies to Redpanda.