1. Release Strategies advanced

    A collaborative product with long-lived client connections needs zero-downtime releases. How do rolling, blue-green and canary differ here?

    2 min answer releasestatefulconnectionscanary
  2. Release Strategies advanced

    A regulated business releases every two weeks through a change advisory board. Engineering wants continuous deployment. The control is real: an auditor tests that every production change was authorised, risk-assessed, tested and reversible. Sequence the migration.

    3 min answer continuous deploymentchange managementauditstandard change
  3. Release Strategies advanced

    At 14:05 a canary on 5% of traffic passes automated analysis across 60 metrics and is promoted. At 14:40 the fleet error rate is 12 times baseline. The canary's own dashboards were clean the entire time. What made the canary blind, and which design decision allowed it?

    3 min answer canaryprogressive deliverystatisticssilent failure
  4. Release Strategies advanced

    You roll back a deployment and the system is still broken. What are the likely reasons?

    2 min answer rollbackmigrationscompatibilitystate
  5. Capacity Planning advanced

    A grocery delivery platform experiences a sudden multi-week increase in demand well beyond any forecast. Which capacity constraints bind first, and which cannot be solved with autoscaling?

    2 min answer capacity-planningdemand-shockmarketplacesupply
  6. Capacity Planning intermediate

    A service runs across three availability zones at 70% CPU during peak. The team wants to survive losing one zone at peak with no user impact. Roughly what does that require, and what does the same arithmetic say about running across two zones?

    3 min answer capacityheadroomavailability zonesstatic stability
  7. Capacity Planning advanced

    Disney+ Hotstar reported a peak of 59 million concurrent viewers during the 2023 cricket World Cup final, having passed 53 million at the semifinal. You are sizing the real-time engagement features for an event in that class. Estimate what the concurrency implies, and say which number decides the architecture.

    3 min answer hotstarconcurrencycapacity planninglive events
  8. Capacity Planning advanced

    How should a platform with extreme scheduled peaks decide how much capacity headroom to hold, and what evidence should drive it?

    2 min answer dream11capacityheadroomforecasting
  9. Capacity Planning advanced

    Your platform runs across three availability zones. How would you determine whether it actually survives losing one?

    2 min answer capacityzone-failureheadroomtesting
  10. Reliability Culture advanced

    An airline's crew-scheduling system cannot re-plan fast enough during cascading weather disruption, forcing manual processes that cannot keep up. What signals indicated this risk earlier, and how should such a system be modernised?

    3 min answer southwestlegacytechnical-debtcapacity
  11. Reliability Culture intermediate

    An organisation adopts blameless postmortems but engineers still avoid admitting mistakes and incidents are under-reported. What is missing beyond the stated policy?

    2 min answer cultureblamelesspsychological-safetyincentives
  12. Reliability Culture advanced

    Roblox's published account of its October 2021 outage describes roughly 73 hours of downtime traced to contention in its Consul cluster, with the telemetry stack depending on the same cluster. Three days is not a technical duration. What organisational conditions turn a software defect into a 73-hour outage, and which are you likeliest to have?

    3 min answer robloxconsulobservabilityincident