Wipro Gcp Data Engineer Interview Questions and Answers

Use SQL to find keys present in table A but not in table B (old copy of A).

• Use a LEFT JOIN to combine tables A and B based on the key column

• Filter the results where the key column in table B is NULL

• This will give you the keys present in table A but not in table B

Use GCP Dataflow to transfer files between GCS buckets

• Create a Dataflow pipeline using Apache Beam to read from source bucket and write to destination bucket

• Use GCS connector to read and write files in Dataflow pipeline

• Set up appropriate permissions for Dataflow service account to access both buckets

Cloud Composer is another orchestration tool in GCP

• Cloud Composer is a fully managed workflow orchestration service built on Apache Airflow

• It allows you to author, schedule, and monitor workflows that span across GCP services

• Cloud Composer provides a rich set of features like DAGs, plugins, and monitoring capabilities

• It integrates seamlessly with other GCP services like BigQuery, Dataflow, and Dataproc

The GCP services used in our project include BigQuery, Dataflow, Pub/Sub, and Cloud Storage.

• BigQuery for data warehousing and analytics

• Dataflow for real-time data processing

• Pub/Sub for messaging and event ingestion

• Cloud Storage for storing data and files

Cloud Functions are event-driven functions that run in response to cloud events.

• Serverless functions that automatically scale based on demand

• Can be triggered by events from various cloud services

• Supports multiple programming languages like Node.js, Python, etc.

To schedule a job to trigger every hour in Airflow, you can use the Cron schedule interval

• Define a DAG (Directed Acyclic Graph) in Airflow

• Set the schedule_interval parameter to '0 * * * *' to trigger the job every hour

• Example: schedule_interval='0 * * * *'

Use Python's slicing feature to display a string in reverse order.

• Use string slicing with a step of -1 to reverse the string.

• Example: 'hello'[::-1] will output 'olleh'.

Pub/Sub is a messaging service that allows communication between independent applications.

• Pub/Sub is used for real-time messaging and event-driven systems.

• It is commonly used for data ingestion, streaming analytics, and event-driven architectures.

• Examples of Pub/Sub services include Google Cloud Pub/Sub, Apache Kafka, and Amazon SNS/SQS.

Google Cloud BigQuery is a fully-managed, serverless data warehouse that uses a distributed architecture for processing and analyzing large datasets.

• BigQuery uses a distributed storage system called Capacitor for storing and managing data.

• It uses a distributed query engine called Dremel for executing SQL-like queries on large datasets.

• BigQuery separates storage and compute, allowing users to scale compute resources ind...read more

List and tuple are both used to store collections of data, but they have some differences.

• Lists are mutable while tuples are immutable

• Lists use square brackets [] while tuples use parentheses ()

• Lists are typically used for collections of homogeneous data while tuples are used for heterogeneous data

• Lists have more built-in methods than tuples

Developed a data pipeline to ingest, process, and analyze customer feedback data for a retail company.

• Used Google Cloud Platform services like BigQuery, Dataflow, and Pub/Sub for data processing.

• Implemented data cleansing and transformation techniques to ensure data quality.

• Created visualizations and dashboards using tools like Data Studio for stakeholders to easily interpret the data.

GCP offers different storage classes for varying performance and cost requirements.

• Standard Storage: for frequently accessed data

• Nearline Storage: for data accessed less frequently

• Coldline Storage: for data accessed very infrequently

• Archive Storage: for data stored for long-term retention

SQL optimization techniques focus on improving query performance by reducing execution time and resource usage.

• Use indexes to speed up data retrieval

• Avoid using SELECT * and instead specify only the columns needed

• Optimize joins by using appropriate join types and conditions

• Limit the use of subqueries and instead use JOINs where possible

• Use EXPLAIN to analyze query execution plans and identify bottlenecks

Window functions in BigQuery are used to perform calculations across a set of table rows related to the current row.

• Window functions allow you to perform calculations on a set of rows related to the current row

• They are used with the OVER() clause in SQL queries

• Common window functions include ROW_NUMBER(), RANK(), and NTILE()

• They can be used to calculate moving averages, cumulative sums, and more

Types of NoSQL databases in GCP include Firestore, Bigtable, and Datastore.

• Firestore is a flexible, scalable database for mobile, web, and server development.

• Bigtable is a high-performance NoSQL database service for large analytical and operational workloads.

• Datastore is a highly scalable NoSQL database for web and mobile applications.

Code to find max number of product by customer

• Iterate through each customer's purchases

• Keep track of the count of each product for each customer

• Find the product with the maximum count for each customer

Creating a dataframe in GCP Data Engineer

• Use the pandas library to create a dataframe

• Provide data in the form of a dictionary or list of lists

• Specify column names if needed

select * from table limit 100 is faster

• Using 'select * from table' retrieves all rows from the table, which can be slower if the table is large

• Using 'select * from table limit 100' limits the number of rows retrieved, making it faster

• Limiting the number of rows fetched can improve query performance

SCD stands for Slowly Changing Dimension and Merge is a SQL operation used to update or insert data in BigQuery.

• SCD is used to track changes to data over time in a data warehouse

• Merge in BigQuery is used to perform insert, update, or delete operations in a single statement

• Example: MERGE INTO target_table USING source_table ON condition WHEN MATCHED THEN UPDATE SET col1 = value1 WHEN NOT MATCHED THEN INSERT (col1, col2)

BigQuery is a fully managed, serverless data warehouse that enables scalable analysis over petabytes of data.

• BigQuery uses a columnar storage format for efficient querying.

• It supports standard SQL for querying data.

• BigQuery allows for real-time data streaming for analysis.

• It integrates with various data sources like Google Cloud Storage, Google Sheets, etc.

• BigQuery provides automatic scaling and high availability.

Dataflow function to split sentence

• Use the Split transform in Dataflow to split the sentence into words

• Apply ParDo function to process each word individually

• Use regular expressions to handle punctuation and special characters

Bigquery is a cloud-based data warehousing tool used for analyzing large datasets quickly. Pubsub is a messaging service, Dataflow is a data processing tool, and Cloud Storage is a scalable object storage service.

• Bigquery is used for analyzing large datasets quickly

• Pubsub is a messaging service used for asynchronous communication between applications

• Dataflow is a data processing tool used for batch and stream processin...read more