GO TO A SECTION

↑ ↓ to navigate · Enter to openExplore all sections →
FDEInterviews logo
← SQL & Data Engineering / 39
hardDatabricksSnowflakePalantir

Design a backfill for an aggregate table that takes late and out-of-order events without double-counting or holes.

The aggregate-restatement problem that breaks naive backfills: events arrive days late and out of order, so any partition you already published may be wrong. The staff answer is event-time partitioning plus bounded restatement, not a bigger watermark.

Updated Aug 2026 · Grounded in real Forward Deployed Engineer interview loops and written to a senior-engineer editorial bar.

The aggregate-restatement problem that breaks naive backfills: events arrive days late and out of order, so any partition you already published may be wrong. The staff answer is event-time partitioning plus bounded restatement, not a bigger watermark.

20 answers per topic instead of 10, plus saved progress and bookmarks · no cardor unlock all 548 remaining answers · ₹2,000 / $25

Every answer, concept and course, every paper breakdown, all published video lessons, hands-on FDE Lab missions, Premium PDF guides and companion files, the full practice-test bank and work-sample downloads. Referral Premium excludes guide PDFs and their companion files.

6 months · One payment · No auto-renewal

Study alongside free video lessons.

Keep practising

Next in this trackModel a dimension bitemporally so you can answer 'what did we believe the customer's plan was, as of last Tuesday?'PremiumNext in this trackJoin two petabyte fact tables where both are skewed on the same key. Neither fits in memory. Make it finish.PremiumNext in this trackYour CDC stream replays a batch and a customer issues a GDPR deletion mid-stream. Keep the silver mirror exactly-once and compliant.Premium
DISCUSSION · 0

No comments yet — be the first to share your approach.