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Adaptive system design practice

DeckedBeta

Daily system design practice for your next interview.

Practice system design trade-offs in five minutes a day

Preparing for a system design interview? Solve short architecture scenarios, compare the wiring, and revisit your weakest topics. Start free, without an account.

  1. Read the scenario. e.g. "A client pushes 1,000 events/s to a downstream service."
  2. Pick an approach. 2-4 options; one fits the constraints best.
  3. Learn the trade-offs. Every card explains why the winner wins and the rest fail.
  4. Study adaptively. Sessions target your weakest topics, and spaced repetition resurfaces cards before you forget.
How cards are made

Cards are generated on the fly with AI assistance and cached for instant reuse, so sessions start without waiting. Cards also stay available on your device for offline review, with seed cards as an offline fallback.

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No account required. Progress is saved in your browser and synchronized with the server using a device identifier, or your account when signed in. Custom cards, bookmarks, and session resume state stay in this browser. Fresh card requests also go through the server.

Try a trade-off

An upload takes 20 seconds to process. Where should the work happen?

Your API must acknowledge accepted uploads within 300 ms. Files must survive worker restarts, and users can check processing status later.

  1. Process the file inside the API request.
  2. Store the file durably, enqueue a job, and let a worker process it.
  3. Return success, then start an in-memory background task in the API process.
Choose an answer, then reveal the trade-off

B fits these constraints. Durable storage and a durable job queue separate acceptance from processing. Return an accepted response with a status URL after durable acceptance; workers must tolerate retries.

Client → API↓ Durable file + jobQueue → Worker → Result

A misses the response budget. C can lose accepted work when the process restarts. If processing took only a few milliseconds, synchronous processing could be simpler.

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Level 1 · Foundations

Name the right building block.

Next: build evidence with your first session.

    Concept lab: make a prediction, then see the system respond.

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    Read the concept on one side, change a constraint on the other, and keep both views in context. Everything is deterministic and educational — it never connects to infrastructure.

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    Find the idea, trade-off, or failure mode behind the experiment.

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    Design Decisions

    The recurring architecture trade-offs behind real systems. Each decision compares the viable options across the criteria that matter, then records the choice and why it wins.

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    Design Decisions

    One architecture decision, its trade-offs, and where to read and practice more.

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