InterviewLayer

System design interview preparation

What are you preparing for?

Pick your interview area. Find the deep dives to study and the question to practise, in a suggested order.

Browse all resources

Suggested starting path

Your infra system design path

3 deep dives, then 1 interview question

Estimated reading: 60 min

Studying for

Mid focus. Follow the working path, preserve the product's promises, and explain the main decision.

The path stays the same. Your focus and reading depth follow you into each lesson.

  1. When to add a queue

    Separate durable acceptance from later telemetry processing.

    What to focus on at Mid

    Derive the async boundary, keep accepted work recoverable, and distinguish waiting space from processing capacity.

    Deep diveEstimated reading: 8 min

  2. Idempotency and retries

    Retry without counting the same measurement twice.

    What to focus on at Mid

    Keep one task distinct from its attempts, save one reply, and handle duplicate work, uncertain outcomes, and late workers safely.

    Deep diveEstimated reading: 11 min

  3. Cursor pagination

    Return large, ordered time ranges page by page.

    What to focus on at Mid

    Continue from a stable indexed position, scope the cursor to the query, and explain what changes between pages can do.

    Deep diveEstimated reading: 7 min
  4. Interview question

    Design a telemetry ingestion and query service

    Register metrics, ingest measurements durably, and find them quickly over a selected time range.

    Question walkthroughEstimated reading: 34 min
Start with When to add a queue Already know these? Go straight to the question

Reading estimates cover the text. Leave extra time for videos, diagrams and working through the design.