Not dev-related, but it's always the every day schedule optimisations that are satisfying. If I need to be in various places throughout the day, change different types of transportation, etc., I always think about the optimal route and time-planning such that I have the least overhead, visit the same place as few times as possible (usually my home, since I live far from most of my daily activities), take the shortest routes and be on time
The same applies to taking public transportation in my hometown. There is no clear schedule ("arrival can vary between 10-15min", no app available to tell you about it in real time), yet by living there for so long, I figured out when certain buses/trams leave based on the ones that are already passing me and the time of the day. This way, I know which buses/trams to take and change and get where I need to be, without even having an app or a clear schedule (of course, unexpected things like buses catching on fire can always happen)