Real Interview Questions

What is the difference between a normal Delta table and a Delta Live Table?

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Delta Lake Delta Live Table Data Engineering

🟡 Medium Conceptual Junior Asked 1× Jun 2026

We have a Delta table `retail_prod.analytics.sales_silver` that is about 600 GB. It is partitioned by `event_date` (daily) and contains many small files (5–20 MB) with no Z‑Order. Dashboards filter on the last 30 days of `event_date` and `merchant_id`, and the p95 query time is above 12 seconds. We cannot change the upstream schema. How can we bring the p95 query time under 12 seconds for the 30‑day window?

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Delta Lake Data Skipping Databricks

🟡 Medium Conceptual Mid Asked 1× May 2026

A Delta‑backed star schema joins one large fact table with several small dimension tables on equality keys. What SQL tactic usually gives the best first‑step speedup?

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Delta Lake Star Schema Broadcast Join

🟡 Medium Conceptual Senior Asked 1× May 2026

Downstream consumers require incremental changes from a Delta table that includes deletes and updates. You must deliver ordered change data capture (CDC) from version checkpoints. Which Delta feature should you use?

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Delta Lake Change Data Feed Cdc

🟡 Medium Conceptual Mid Asked 1× May 2026

You are planning schema evolution where columns may be added and reordered. You want reliable column mapping for long‑term merges. Which setting is appropriate?

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Delta Lake Schema Evolution Column Mapping

🟡 Medium Conceptual Mid Asked 1× May 2026

Analysts filter a 2‑TB Delta table by event_date and customer_id. You see high data‑skipping misses due to out‑of‑order loads. What is the most targeted improvement?

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Delta Lake Data Skipping Z-ordering Partitioning

🟡 Medium Conceptual Mid Asked 1× May 2026

Can you tell me what vacuum is in Databricks?

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Databricks Delta Lake Data Engineering

🟡 Medium Conceptual Junior Asked 1× Apr 2026