One example would be a video game, full of subsystems that all operate with different notions of time — networking code working in terms of packets with variable ping, physics locked at 60hz, gameplay logic happening at various rates (some stuff is every frame, some stuff is once every few frames, some stuff goes into a low-priority queue, some stuff happens at specific moments), rendering synced to the display refresh interval, audio happening both in sync with the gameplay logic but also at the audio sampling rate, and on and on. These subsystems are kinda isolated, but they're also kinda interdependent. There could be a lot of shared state, or a lot of dynamism in how these subsystems affect one another, or a lot of design decisions that prioritize performance at all costs. Ultimately, the code needs to be quite deterministic and very well understood in order to ensure that the game runs quickly and correctly, and you don't (can't?) have automated tests or static verification, so you generally have to work on it by loading it all into your head.
(I hope I'm understanding your question correctly. Sorry if this is not what you had in mind.)