Data Engineering Fundamentals 2

Question 1

What is the primary difference between ETL and ELT?

Accepted Answer

ETL transforms data before loading into the target; ELT loads raw data first then transforms inside the target

Answer

In ETL transformation happens before loading, while in ELT raw data is loaded first and transformed within the destination system.

Question 2

Which file format is columnar and optimized for analytical query performance?

Accepted Answer

Parquet

Answer

Parquet stores data by column, enabling efficient compression and fast analytical reads.

Question 3

What does idempotency mean for a data pipeline task?

Accepted Answer

Running the task multiple times produces the same result as running it once

Answer

An idempotent task yields the same outcome no matter how many times it is executed, preventing duplicate side effects.

Question 4

In a star schema, the central table that holds measurable business events is called the:

Accepted Answer

Fact table

Answer

The fact table sits at the center of a star schema and stores quantitative metrics referencing surrounding dimension tables.

Question 5

Which tool is most commonly used to orchestrate and schedule batch data workflows as DAGs?

Accepted Answer

Apache Airflow

Answer

Apache Airflow defines workflows as directed acyclic graphs (DAGs) and schedules their execution.

Data Engineering Practice Test