1. 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
  2. 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
  3. 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
  4. 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
  5. 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
  6. Saga advanced

    A multi-party booking saga is running in production and support cannot answer where a particular booking is. What is missing from the implementation?

    2 min answer shiprocketsagaobservabilitystate
  7. Saga advanced Multiple choice

    An order flow spans several services and cannot use a distributed transaction. What decides between orchestration and choreography for the saga?

    2 min answer sagaorchestrationchoreographycompensation
  8. Saga advanced

    An order spans payment, inventory and shipping, each in its own service with its own database. How do you keep them consistent?

    3 min answer sagaconsistencycompensationoutbox
  9. Saga advanced

    Design an order saga: reserve inventory, take payment, dispatch shipment, send confirmation. What ordering problem do you see?

    2 min answer sagacompensationdesign
  10. Saga intermediate

    Review this. A grocery-fulfilment platform in the mould of Instacart runs an orchestrated saga over five steps - cart freeze, pricing, promotion, loyalty accrual, order creation - each with a compensating action, driven by an orchestrator with its own saga log. All five services are owned by one team, deployed as one binary, and write to five schemas in one Postgres cluster. What would you remove, and what would you leave alone?

    3 min answer sagacompensationtransactionssimplification
  11. Service Mesh advanced

    A platform is evaluating a service mesh. What should be checked before adopting, and what is the honest justification?

    2 min answer service-meshcomplexityobservabilitymtls
  12. Service Mesh advanced

    A platform runs 2000 pods across 300 services and is about to put a sidecar proxy in every pod. Roughly what does the fleet cost in memory and control-plane work before a single request is served, and which number grows fastest as the platform doubles?

    3 min answer service meshsidecarcapacitycontrol plane