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Netflix interview themes
What people report studying for — not a take-home dump. Last editorial update 2026-07-20.
Rounds you should expect
SQL / Spark
Sessionize playback events with a gap. Event time vs processing time. Why floored timestamps are wrong.
Streaming
Consumer lag SLO, late events, and what you drop when the watermark moves.
Recently added questions
2026-09-05 · Processing time after an outage
The source was down six hours. Processing-time windows then show a spike. What actually happened?
Events were bucketed when they were processed, not when they occurred. Event-time plus watermarks put counts on the real hour. The spike is a lie.
From the question bank
easy · SQL · SQL
Sessionize click events with a 30-minute inactivity gap.
Practice →medium · SQL · SQL
You need a 7-day rolling unique users. What breaks if you use COUNT DISTINCT in a window carelessly?
Practice →medium · SQL · SQL
You grouped by DATE_TRUNC(week, ts) and compared to last week. Why are week 1 and week 53 lying?
Practice →medium · Warehouse · Snowflake
Micro-partitions and clustering: when does a clustering key pay for itself?
Practice →hard · Orchestration · Airflow
A load task appends. The retry doubled yesterday. What was missing?
Practice →medium · Orchestration · Airflow
You need a backfill of 400 days. How do you not strand the 08:00 DAG?
Practice →easy · Warehouse · Databricks
A shuffle-heavy join OOMs the worker. Name three levers before you “just scale the cluster.”
Practice →medium · Warehouse · Databricks
You VACUUMed with a 7-day retention and a reader is on an 8-day-old notebook. What happens?
Practice →easy · Streaming · Kafka
Kafka vs Kinesis — what is the real trade?
Practice →medium · Coding · Spark
Driver vs executor. Where does your Python UDF actually run?
Practice →medium · Coding · Spark
Kryo vs Java serialization. When do you care?
Practice →hard · Coding · Spark
S3 vs HDFS locality. Why was the same job faster on HDFS?
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