Ship-it checklist (all 4 deliverables)
- Lab 1: idempotent Parquet ETL, date partitions, README counts + plan.
- Lab 2: MERGE upserts, time-travel + RESTORE evidence, OPTIMIZE proof.
- Lab 3: partition evolution without rewrite, pruning + rollback evidence.
- Redpanda mini: kill/restart with count == 1000, zero duplicates.
The 5 interview one-liners
- Lazy transforms + actions; narrow vs wide (shuffle) transforms.
- Partition on filter columns with modest cardinality; prune, don't scan.
- Parquet = format; Delta/Iceberg = Parquet + log giving ACID/MERGE/travel.
- OPTIMIZE compacts, VACUUM deletes โ never vacuum inside your travel window.
- Iceberg hidden partitioning decouples logical values from paths: evolve freely.
Where next
- Orchestrate these jobs (Airflow/Dagster) with partition-aware backfills.
- Serve the gold layer (dbt models on top of Delta/Iceberg).
- Table health SLIs: file counts, snapshot age, stream lag โ alert on drift.