Wednesday, February 1, 2023

Walmart Data Engineer 3 Interview Questions

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What Is The Purpose Of A/b Testing

Walmart Labs SQL Interview Question for Senior Data Analyst Position | Data Analytics

A/B testing is a randomized experiment performed on two variants, A and B. It is a statistics-based process involving applying statistical hypothesis testing, also known as two-sample hypothesis testing. In this process, the goal is to evaluate a subjects response to variant A against its response to variant B to determine which variants are more effective in achieving a particular outcome.

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What Is An Alias In Sql

An alias enables you to give a table or a particular column in a table a temporary name to make the table or column name more readable for that specific query. Aliases only exist for the duration of the query.

The syntax for creating a column alias

SELECT column_name AS alias_name

The syntax for creating a table alias

SELECT column_name

FROM table_name AS alias_name

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What Is A Trigger In Sql

In SQL, a trigger refers to a set of statements in a system catalog that runs whenever DML commands run on a system. It is a special stored procedure that gets called automatically in response to an event. Triggers allow the execution of a batch of code whenever an insert, update or delete command is executed for a specific table. You can create a trigger by using the CREATE TRIGGER statement. The syntax is:

CREATE TRIGGER trigger_name

ON table_name FOR EACH ROW

BEGIN

END

What Is A Cursor

Electrical and Electronics Engineer Red

A cursor is a temporary memory or workstation. It is allocated by the server when DML operations are performed on the table by the user. Cursors store Database tables. SQL provides two types of cursors which are:

  • Implicit Cursors: they are allocated by the SQL server when users perform DML operations.

  • Explicit Cursors: Users create explicit cursors based on requirements. Explicit cursors allow you to fetch table data in a row-by-row method.

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What Are The Benefits Of Using Aws Identity And Access Management

  • AWS Identity and Access Management supports fine-grained access management throughout the AWS infrastructure.

  • IAM Access Analyzer allows you to control who has access to which services and resources and under what circumstances. IAM policies let you control rights for your employees and systems, ensuring they have the least amount of access.

  • It also provides Federated Access, enabling you to grant resource access to systems and users without establishing IAM Roles.

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What Is Your Approach To Developing A New Analytical Product As A Data Engineer

The hiring managers want to know your role as a data engineer in developing a new product and evaluate your understanding of the product development cycle. As a data engineer, you control the outcome of the final product as you are responsible for building algorithms or metrics with the correct data.

Your first step would be to understand the outline of the entire product to comprehend the complete requirements and scope. Your second step would be looking into the details and reasons for each metric. Think about as many issues that could occur, and it helps you to create a more robust system with a suitable level of granularity.

Have You Worked With Etl If Yes Please State Which One Do You Prefer The Most And Why

Walmart Interview Experience | Software Engineering | 5+ Backend Developer

With this question, the recruiter needs to know your understanding and experience regarding the ETL tools and process. You should list all the tools in which you have expertise and pick one as your favourite. Point out the vital properties which make that tool stand out and validate your preference to demonstrate your knowledge in the ETL process.

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Walmart Data Engineer Interview Questions

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713.0KApplication

I applied through other source. The process took 3 weeks. I interviewed at Walmart in Aug 2021

Interview

I participated in the virtual event where I had 2 interviews – one with a manager and one with a senior developer. After tht I was contacted by the recruiter for a final panel round of interview with three managers. All interviews were technical

Interview Questions

What Are The Various Types Of Load Balancers Available In Aws

  • An Application Load Balancer routes requests to one or more ports on each container instance in your cluster, making routing decisions at the application layer . It also enables path-based routing and may route requests to one or more ports on each container instance in your cluster. Dynamic host port mapping is available with Application Load Balancers.

  • The transport layer is where a Network Load Balancer decides the routing path. It processes millions of requests per second, and dynamic host port mapping is available with Network Load Balancers.

  • Gateway Load Balancer distributes traffic while scaling your virtual appliances to match demands by combining a transparent network gateway.

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    What Challenges Came Up During Your Recent Project And How Did You Overcome These Challenges

    Any employer wants to evaluate how you react during difficulties and what you do to address and successfully handle the challenges.

    When you talk about the problems you encountered, frame your answer using the STAR method:

    • Situation: Brief them about the circumstances due to which problem occurred.
    • Task: It is essential to elaborate on your role in overcoming the problem. For example, if you took a leadership role and provided a working solution, then showcasing it could be decisive if you were interviewing for a leadership position.
    • Action: Walk the interviewer through the steps you took to fix the problem.
    • Result: Always explain the consequences of your actions. Talk about the learnings and insights gained by you and other stakeholders.

    Are Lookups Faster With Dictionaries Or Lists In Python

    Civil Engineer

    The time complexity to look up a value in a list in Python is O since the whole list iterates through to find the value. Since a dictionary is a hash table, the time complexity to find the value associated with a key is O. Hence, a lookup is generally faster with a dictionary, but a limitation is that dictionaries require unique keys to store the values.

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    What Skills Does A Data Engineer Need

    Below are some essential skills that a data engineer or any individual working in the data engineering field requires-

  • SQL: Data engineers are responsible for handling large amounts of data. Structured Query Language is required to work on structured data in relational database management systems . As a data engineer, it is essential to be thorough with using SQL for simple and complex queries and optimize queries as per requirements.

  • Data Architecture and Data Modeling: Data engineers are responsible for building complex database management systems. They are considered the gatekeepers of business-relevant data and must design and develop safe, secure, and efficient systems for data collection and processing.

  • Data Warehousing: It is important for data engineers to grasp building data warehouses and to work with them. Data warehouses allow the aggregation of unstructured data from different sources, which can be used for further efficient processing and analysis.

  • Programming Skills: The most popular programming languages used in Big Data Engineering are Python and R, which is why it is essential to be well versed in at least one of these languages.

  • Microsoft Excel: Excel allows developers to arrange their data into tables. It is a commonly used tool to organize and update data regularly if required. Excel provides many tools that can be used for data analysis, manipulation, and visualization.

  • What Are Some Biases That Can Happen While Sampling

    Some popular type of bias that occurs while sampling is

    • Undercoverage- The undercoverage bias occurs when there is an inadequate representation of some members of a particular population in the sample.

    • Observer Bias- Observer bias occurs when researchers unintentionally project their expectations on the research. There may be occurrences where the researcher unintentionally influences surveys or interviews.

    • Self-Selection Bias- Self-selection bias, also known as volunteer response bias, happens when the research study participants take control over the decision to participate in the survey. The individuals may be biased and are likely to share some opinions that are different from those who choose not to participate. In such cases, the survey will not represent the entire population.

    • Survivorship Bias- The survivorship bias occurs when a sample is more concentrated on subjects that passed the selection process or criterion and ignore the subjects who did not pass the selection criteria. Survivorship biases can lead to overly optimistic results.

    • Recall Bias- Recall bias occurs when a respondent fails to remember things correctly.

    • Exclusion Bias- The exclusion bias occurs due to the exclusion of certain groups while building the sample.

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    What Do You Understand About Threads In The Context Of Operating Systems What Do You Know About Multi

    Within a process, a thread is a path of execution. Multiple threads can exist in a process. A thread is the smallest unit of processing and is a lightweight sub-process.

    Multithreading refers to the process of running multiple threads simultaneously in a process. By dividing a process into many threads, parallelism can be achieved. Multiple tabs in a browser, for example, can represent different threads. MS Word makes use of numerous threads: one to format the text, another to receive inputs, and so on. Below are some more advantages of multithreading.

    The following are the advantages of multithreading:

    What Do You Mean By U

    Zero Experience to a DATA Engineer @ WALMART ð¥ 250% CTC Hike ð¥MAANG interview process
    • Azure Data Lake Analytics uses U-SQL as a big data query language and execution infrastructure.

    • U-SQL scales out custom code from a Gigabyte to a Petabyte scale using typical SQL techniques and language.

    • Big data processing techniques like “schema on reads,” custom processors, and reducers are available in U-SQL.

    • The language allows you to query and integrate structured and unstructured data from various data sources, including Azure Data Lake Storage, Azure Blob Storage, Azure SQL DB, Azure SQL Data Warehouse, and SQL Server instances on Azure VMs.

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    What Are The Advantages Of Multithreading Over Multiprocessing

    Some advantages of multithreading are:

    • Improved responsiveness: Helps in increasing the responsiveness in the system as there are several threads, and even if some of these get blocked, the others might continue their execution.
    • Reduced switch context time: When it comes to threads, context switching is faster as these threads have the same data and code. The only differentiating factor for each thread is the stacks.
    • Better communication: As all the threads are present in just a single process, the communication among the threads is much easier as compared to that of processes.

    What Is The Difference Between Append And Extend In Python

    The argument passed to append is added as a single element to a list in Python. The list length increases by one, and the time complexity for append is O.

    The argument passed to extend is iterated over, and each element of the argument adds to the list. The length of the list increases by the number of elements in the argument passed to extend. The time complexity for extend is O, where n is the number of elements in the argument passed to extend.

    Consider:

    List1 will now be : ]

    The length of list1 is 4.

    Instead of append, use extend

    list1.extend

    List1 will now be :

    The length of list1, in this case, becomes 6.

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    Faqs On Walmart Software Engineer Interview Questions

    Q1. Is it difficult to crack Walmart interview?

    While it is not as hard as cracking the tech interviews at FAANG, itâs not easy as well. Just remember to go over the given topics and practice your coding. If you prepare well, you can easily pass the interview.

    Q2. What questions do they ask at the Walmart interview?

    Some questions you can expect in the interview are â Why are you the perfect fit for this position? Why do you want to work at Walmart? If there was a time crunch, how would you ensure that the quality of your work doesnât suffer?

    Q3. What do software engineers at Walmart do?

    As a software engineer at Walmart, youâll be responsible for technical discovery, design, and implement large-scale applications, products, and platforms. Youâll be working with and reporting to the manager of software engineering.

    Q4. How to prepare for a Walmart interview?

    The first thing to do is to research the role as thoroughly as you can. Make sure that you study the core values of Walmart, prepare CS fundamentals, practice coding, and donât forget to prepare for the HR rounds.

    Q5. Whatâs the salary of a senior software engineer at Walmart?

    As per Indeed.com, a senior software engineer at Walmart makes around $126,386 per year on average.

    Walmart Interview Experience For Sde

    Mechanical Design Engineer Red

    I applied via referral from LinkedIn. I got a call from the HR team for scheduling an interview.

    Round 1 : .

    Round 2 : This round started with a brief introduction, followed by 2 coding questions.

    • Next Greater ElementFirst I explained him my understanding about the question and then implemented brute force code for the problem and then he asked about the complexity of the solution and also to optimize the solution. I was able to do that.
    • Sort a nearly sorted arraySame process as the first question. Different is just that here I got confused with the complexity of optimised code. Later I was able to explain that as well.

    We finished the above 2 questions in 45 min, however interview was for 1 hour, so the interviewer asked about algorithms and their complexity and there use cases related to sorting like insertion sort, merge sort, quick sort, etc.

    Round 3 : The interviewer was very polite and very formal.

    Round 4 :

    Round 5 :

    Verdict :

    Overall interviews were very good. After 2 weeks finally got a very good offer.

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    Data Engineer Interview Questions On Sql

    You will spend most of your career using SQL if you are a Data Engineer working in an organization. Building a strong foundation in SQL is crucial since you may easily save time and effort if you can leverage its various features effectively. Also, acquire a solid knowledge of databases such as the NoSQL or Oracle database. Questions addressing data modeling and database architecture test your understanding of entity-relationship modeling, normalization and denormalization, dimensional modeling, and relevant ideas. Below are a few data engineer interview questions on SQL concepts, queries on data storage, data retrieval, and a lot more.

    Prepare For Your Data Engineer Interview

    To prepare for your interview, you may find confidence in reviewing everything youâve learned from previous roles and courses youâve taken. Imagine yourself in the interview, whether it is in person or over Zoom, with the hiring manager asking you technical questions.

    • Study and master SQL. Review data pipeline systems and emerging technologies in the Hadoop ecosystem.

    • Design a sample data pipeline. Make sure you understand the objective, and how you factor in data lineage, data duplication, loading data, scaling, testing, and end-user access patterns.

    • Learn and review languages. Look at the job description to understand what the role entails. For backend-oriented systems, youâll want to know Scala, and for analytics and data science-oriented systems, youâll want to be well-versed in Python.

    • Research potential interview questions. Besides those listed above, you may be able to find interview questions for the company on Glassdoor. Itâs worth peeking there as part of your prep, in case someone has kindly made that advice available to the public.

    • Talk through your process. This is perhaps the most important tip of all. Knowing how to write code and assemble data is not enough, you must be able to communicate your process and decision-making to the interviewers. Practice by talking through a recent project to a friend who is unfamiliar with big data.

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    Mention Some Differences Between The Delete And Truncate Statements In Sql

    DELETE command

    TRUNCATE command

    The DELETE command helps to delete one specific row or more than one row corresponding to a certain condition.

    The TRUNCATE command helps to delete all rows of a table.

    It is a Data Manipulation Language command.

    It is a Data Definition Language command.

    In the case of the DELETE statement, rows are removed one at a time. The DELETE statement records an entry for each deleted row in the transaction log.

    Truncating a table removes the data associated with a table by deallocating the data pages that store the table data. Only the page deallocations get stored in the transaction log.

    The DELETE command is slower than the TRUNCATE command.

    The TRUNCATE command is faster than the DELETE command.

    You can only use the DELETE statement with DELETE permission for the table.

    Using the TRUNCATE command requires ALTER permission for the table.

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