1. Data Lifecycle & Retention advanced

    A GDPR erasure request arrives for a customer. Where does their data actually live, and what makes this expensive to retrofit?

    2 min answer gdprerasureprivacylifecycle
  2. Data Lifecycle & Retention advanced

    A consumer fintech accumulates transaction, behavioural and derived data. How should retention, archival, deletion and regulatory holds be designed so they do not conflict?

    2 min answer credretentiondeletionlegal-hold
  3. Data Lifecycle & Retention advanced

    A customer exercises their right to erasure. List every place their data plausibly exists in a mature architecture and how each is handled.

    3 min answer lifecycledeletiongdprbackups
  4. Data Lifecycle & Retention advanced

    A file storage platform must permanently delete a user's data on request, while maintaining backups, replicas, caches and search indexes. What makes this genuinely difficult, and how is it designed?

    3 min answer data-lifecycledeletionbackupscrypto-shredding
  5. Data Warehousing advanced

    A finance report double-counts revenue after a new fact table is added. What is the likely modelling error?

    2 min answer warehousegrainfan-outdimensional-modelling
  6. Data Warehousing advanced

    A travel platform runs thousands of experiments simultaneously and needs its warehouse to support reliable analysis. What warehouse design decisions prevent cross-experiment contamination and infrastructure artefacts from being read as results?

    2 min answer warehouseexperimentationdata-modellingbooking
  7. Data Warehousing intermediate

    An analytics platform separates compute from storage. What does that actually buy architecturally, and what problems does it not solve?

    2 min answer snowflakecompute-storageisolationconcurrency
  8. Data Warehousing intermediate

    Finance and marketing report different revenue for the same month from the same warehouse. Where do you look and what would have prevented it?

    2 min answer warehouseconformed-dimensionsdefinitionswalmart
  9. ETL & ELT advanced

    A daily pipeline has been producing wrong numbers for three weeks due to a logic bug. What must be true of the architecture for the fix to be a one-day job?

    3 min answer eltbackfillidempotencyairflow
  10. ETL & ELT intermediate

    A grocery platform ingests catalogue and inventory feeds from hundreds of retailers, each with different formats, quality and update frequency. Should transformation happen before loading or after, and where should data quality be enforced?

    2 min answer etleltdata-qualityingestion
  11. ETL & ELT intermediate

    A nightly pipeline failed halfway and the retry produced duplicate rows. Walk me through fixing this properly.

    2 min answer idempotencypipelinesbackfillcorrectness
  12. Event Sourcing advanced

    A brokerage proposes event sourcing for its account ledger. What requirements would genuinely justify it, and when is conventional state plus an audit trail the safer choice?

    2 min answer growwevent-sourcingauditledger