Question 1

Which command displays the current working directory in a Linux terminal?

Accepted Answer

The pwd (print working directory) command displays the absolute path of the current directory. It is essential for locating oneself in the file tree, especially when navigating between multiple folders or in bash scripts.

Question 2

Which command initializes a new Git repository in an existing directory?

Accepted Answer

The git init command creates a new Git repository in the current directory by initializing the .git subdirectory containing all files needed for versioning. This command is the first step to start tracking changes in an existing project.

Question 3

What is a class in Python?

Accepted Answer

A class is a blueprint that defines the structure and behavior of objects. It encapsulates data (attributes) and functions (methods) that operate on that data. Classes allow creating multiple instances sharing the same structure but with different values, which is fundamental to object-oriented programming.

Question 4

What is a Docker container?

Accepted Answer

A Docker container is a runnable instance of a Docker image. It encapsulates an application and all its dependencies in an isolated and portable environment. Unlike virtual machines, containers share the host system's kernel, making them much lighter and faster to start. Each container has its own filesystem, network stack, and isolated processes.

Question 5

What is a Data Lake?

Accepted Answer

A Data Lake is a centralized storage system capable of storing raw data in its native format, whether structured, semi-structured, or unstructured. Unlike a Data Warehouse which imposes a schema at write time (schema-on-write), a Data Lake applies schema at read time (schema-on-read), offering maximum flexibility for data exploration and analysis.

Question 6

What storage architecture does BigQuery use?

Accepted Answer

BigQuery uses a serverless architecture with columnar storage called Capacitor. This architecture separates storage and compute, enabling independent scaling and separate billing. Columnar storage is optimized for analytical queries as it allows reading only the required columns, significantly reducing I/O.

Question 7

Which PostgreSQL configuration file contains main server parameters like shared_buffers and work_mem?

Accepted Answer

The postgresql.conf file contains the main PostgreSQL server configuration parameters, including memory allocations (shared_buffers, work_mem), connection settings, logging, and performance tuning. This file is read at server startup and some parameters require a full restart to take effect.

Question 8

In dbt, what is the main purpose of Jinja macros?

Accepted Answer

Jinja macros enable code reuse across multiple dbt models. They work like functions that accept parameters and return dynamically generated SQL code. This avoids code duplication and makes it easier to maintain complex transformations throughout the project.

Question 9

What is the main difference between ETL and ELT?

Accepted Answer

In ETL (Extract-Transform-Load), data is transformed on an intermediate server before being loaded into the destination. In ELT (Extract-Load-Transform), raw data is first loaded into the destination (typically a cloud data warehouse), then transformed directly within it using its compute power. ELT has become popular with cloud data warehouses like BigQuery, Snowflake or Redshift that offer elastic compute power.

Question 10

What is the main role of a Sensor in Apache Airflow?

Accepted Answer

A Sensor is a special operator that waits for a condition to be met before continuing DAG execution. It periodically checks (pokes) whether the condition is satisfied, such as file arrival, partition availability, or another task's state. Sensors are essential for orchestrating workflows dependent on external events.

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