MockDojo

Question bank, System design, Top system design

Design a distributed job scheduler

Design a service that runs millions of scheduled and recurring jobs reliably.

45 minutes, for mid-level, senior engineers

How the interview runs

  1. 1.Requirements. Before we design anything: what are the core functional requirements, and which non-functional ones matter most here?
  2. 2.Estimates. Let's size it. Assume 10M jobs a day, some recurring every minute.
  3. 3.API + data model. What does the API look like, and how would you model and store the data?
  4. 4.High-level design. Walk me through the high-level architecture, request by request.
  5. 5.Deep dive. How do you guarantee each job runs once, on time, even when workers crash?
  6. 6.Trade-offs + failure. What are the main trade-offs you made, and what happens when a component fails?

What you're graded on

  • Clarified requirements15 pts
  • Back-of-envelope estimates10 pts
  • Clear API10 pts
  • Data model + storage choice15 pts
  • Coherent architecture15 pts
  • Exactly-once-ish execution20 pts
  • Trade-offs8 pts
  • Failure handling7 pts

Practice this one for real

Answer it phase by phase, then get the rubric score, what you missed and the model answer outline.

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