Category

Systems explainers

The rules that hold under load: scheduling, queues, ordering, caching, and the failures that arrive when a system gets busy.

10 interactive explainers. Each one is a visual story with a live simulation and a knowledge check, and the Ask ViLearn tutor beside all three. Free, and nothing requires an account.

• The secret lives of deleted files

  rm feels like destruction. The name vanishes and the space comes back. But almost nothing is destroyed.

  Beginner · 9 min · Story, simulation and quiz

• Jury duty for servers

  No machine is in charge in advance. Any of them can lag or crash. Even so, the cluster returns a single ordered history that every server replays the same…

  Advanced · 12 min · Story, simulation and quiz

• Why a log beats a queue when two teams want the same event

  A queue hands the message to whoever asks first, and then it is gone. Kafka hands nothing over — it appends to a file that only grows, and each reader…

  Intermediate · 11 min · Story, simulation and quiz

• The multitasking illusion

  A music player, a browser and a download, all running 'at the same time'. On a single core, none of them are.

  Beginner · 9 min · Story, simulation and quiz

• How a cluster decides which server holds your data

  Picking a server with hash % N looks obvious and works fine — until N changes.

  Intermediate · 10 min · Story, simulation and quiz

• How your operating system fakes an entire computer

  Every program on your machine believes it owns the entire CPU and all of memory. None of them do.

  Intermediate · 11 min · Story, simulation and quiz

• What a queue really does when you are overloaded

  Work arrives 10% faster than you finish it. Throughput stays flat, errors stay at zero, and nothing on the dashboard goes red.

  Intermediate · 10 min · Story, simulation and quiz

• Why a road turns red without anyone counting a car

  The road on your screen is red. Nothing on it has been counted. The map is built from phones that share their location.

  Intermediate · 11 min · Story, simulation and quiz

• Why one expired key takes down a database that was 20% busy

  A cache serves 99 of every 100 reads. The database behind it has never seen more than a trickle.

  Advanced · 11 min · Story, simulation and quiz

• Why the ride you get is not the nearest car

  A rider taps Request and expects a name, a photo and an arrival time in about three seconds.

  Advanced · 12 min · Story, simulation and quiz

Other categories: Networking · Deployment & Cloud · Databases & Search · Developer Tools · AI & Machine Learning
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