1. Real-Time Serving Layer advanced

    A feature needs personalised results in under 50 ms for millions of users. What is computed when?

    2 min answer servingprecomputationhybridfreshness
  2. Real-Time Serving Layer advanced

    A flash sale opens at a published time. The precomputed inventory and price data is served from a real-time serving layer whose caches were rebuilt an hour earlier during a deploy. What happens in the first ten seconds after the sale opens?

    3 min answer flash salecold cacherequest collapsingalibaba
  3. Real-Time Serving Layer intermediate Multiple choice

    A product page needs the current computed price for one product id at 40,000 reads per second with p99 under 25 ms. A stream processor already recomputes each product's price every few seconds from competitor and inventory events. Where should the read path go?

    3 min answer serving-layerkey-valuequeryable-stateolap
  4. Real-Time Serving Layer advanced

    A real-time platform must serve computed state to a low-latency request path. What should the serving layer look like?

    2 min answer serving-layerdecouplingfreshnessavailability
  5. Real User Monitoring intermediate

    A content platform's synthetic tests pass and users report slowness. What monitoring closes the gap?

    2 min answer pratilipirumfield-datasegmentation
  6. Real User Monitoring advanced

    A team's synthetic monitoring is green and users report the site is slow. What is the monitoring missing?

    1 min answer rumsyntheticpercentilessegmentation
  7. Real User Monitoring beginner

    Interaction to Next Paint replaced First Input Delay as a Core Web Vital on 12 March 2024. A site that passed FID comfortably can fail INP badly. What did FID measure, what does INP measure, and why does the change match user complaints better?

    3 min answer inpfidcore-web-vitalsrum
  8. Real User Monitoring advanced Multiple choice

    Real user monitoring shows p75 largest contentful paint at 2.1 seconds - comfortably inside target - while a marketing analysis shows a real drop in conversion from organic mobile traffic. Which measurement artefact most likely explains the gap?

    3 min answer rumsurvivorship-biasmeasurementsampling
  9. Real-Time Analytical Stores intermediate Multiple choice

    A creator analytics feature must show per-minute view counts for 8 million creators over a 90-day window at p95 under 500 ms while ingesting 300 thousand view events per second. Work out the row counts and decide which storage shape fits.

    3 min answer rollupretentioncolumnarsizing
  10. Real-Time Analytical Stores advanced

    A platform needs sub-second analytical queries over a continuously updating dataset. What kind of store, and what are the trade-offs?

    2 min answer zerodhaolapingestionfreshness
  11. Real-Time Analytical Stores advanced

    A platform needs sub-second analytical queries over recent high-volume event data. What store characteristics matter?

    2 min answer realtime-analyticsingestioncardinalityretention
  12. Real-Time Analytical Stores intermediate Multiple choice

    A team proposes a specialised real-time analytics store for an internal dashboard used by twelve analysts. Assess.

    2 min answer architecturecostdecision