1. Publish/Subscribe advanced

    A chat platform uses publish/subscribe to deliver messages to connected clients. What breaks when a channel has a million members, and what changes?

    2 min answer pubsubfan-outscalepresence
  2. Publish/Subscribe advanced Multiple choice

    A payments service publishes PaymentCaptured to a topic with four subscribers. A fifth team needs the same event plus the payer's full name and address, which the producer does not emit because those fields are restricted. The fifth team proposes subscribing and then calling the producer per event to fetch them - about 900 extra reads a second. Which design fits?

    3 min answer pub-subtopic designauthorisationpii
  3. Publish/Subscribe advanced Multiple choice

    A social feed becomes too expensive to generate at read time. Should the system fan out on write, fan out on read, or use a hybrid - and what decides it?

    2 min answer fanoutfeedscelebrity-problemmeta
  4. Publish/Subscribe intermediate

    A team must choose between publish-subscribe and a work queue for a new integration. What distinguishes them, and which failure mode does each have?

    2 min answer confluentpubsubqueuefanout
  5. Publish/Subscribe advanced

    An interviewer says - design the delivery path for a live cricket scorecard to a peak concurrent audience of the size Hotstar reported for the 2023 World Cup final, around 59 million. Walk me through the clarifying questions that change the design, then your first architecture.

    3 min answer fan-outlive eventspubsubcdn
  6. Publish/Subscribe advanced

    In a team chat product, a message posted to a channel with 8,000 members must reach everyone connected. Design the delivery path.

    2 min answer slackmessagingwebsocketsfanout