If I had chance I would really like to take a look at system architecture hashnode itself since it's a really nice platform for developers.If I could understand the api docs well, the first thing I would do is port the website to android/ios app because correct me if I am wrong but I could not find android app of hashnode on playstore and really would like to have one instead of accessing the site on mobile browser when I am on the go.
Even if I had a chance I would not touch the systems/software platforms of big companies because they might too complex for me to understand in a span of 24 hours and even if I did understand them I won't change them at all for any selfish purpose since many developers just like us have worked really hard to create such major products and it really does not make any sense to make their efforts go in vain just to fulfill our own selfish gains.