Scaling down
Software engineers think about scaling up a lot: how will this system handle more data or more traffic? This makes us think about scale in other contexts. It applies to pastimes, for example: I find that running scales fairly poorly, at least for me. The better I get at it, the more time it takes, but I find it hard to run frequently while avoiding injury. Excellent literature tends to scale well: reading twice as much gives you more than twice the return.
But we sometimes forget to think about scaling down. How will things work if you have less energy, time, or money to put into them? This question is important to me these days, when discretionary time can be unpredictable.
Trivia, as it happens, is great along this dimension. I can make real progress in flashcarding in even one minute or less. (Yes, perhaps just taking a deep breath would be better, but I do that too with some of my spare minutes, and among relevant competitors on my phone for my attention, flashcarding gives me a much higher return.) In fact, I don't know of any hobby that better rewards very small, randomly distributed time investments. If you do, please write to me and tell me.