StockX Data Engineer Interview Questions and Answers

Q1. Questions on Past Project
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Q2. SQL Dense Rank - also having the option to do in Pandas
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Q3. Pandas groupby on a dataset given - required to calculate group wise yoy rate of a column
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Q1. Past project ( which he chose , he chose my very first project , which I had forgotten) so ended up screwing it
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Q2. SQL / Pyspark question - difficult question
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Q1. DSA question with Some Stack
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Q2. Discussion around Current project
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Q1. Managerial discussion around resume and some basic java and spring question
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Q2. Java and spring boot question
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Q1. Asked to write a program to check whether string is valid or not. String consists of only three kind of special characters "(), [], {}". We need to return true if all special characters are in correct for...read more
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Q2. What is useRef hook used for?
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useRef hook is used to persist a mutable value across renders without causing a re-render.
• Used to store mutable values that do not trigger re-renders.

• Commonly used for accessing DOM elements or storing previous values.

• Does not cause a re-render when the value changes.
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Q3. What are the best practices to avoid rerenders and to improve performance
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Use memoization, virtual DOM, and shouldComponentUpdate to avoid unnecessary rerenders and improve performance.
• Implement memoization to store the result of expensive function calls and avoid recalculating them.

• Use virtual DOM to efficiently update only the parts of the UI that have changed.

• Override shouldComponentUpdate to prevent unnecessary rerenders by comparing current and next props/state.
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Q4. What are callbacks, Promises, async await
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Callbacks, Promises, async await are asynchronous programming concepts in JavaScript.
• Callbacks are functions passed as arguments to another function to be executed later.

• Promises are objects representing the eventual completion or failure of an asynchronous operation.

• async await is a syntax for writing asynchronous code that looks synchronous, making it easier to read and maintain.

• Example: Using a callback to handle th...read more
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Q1. Interviewer asked me basic SQL questions
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Q2. In the second technical round he asked me advanced SQL topics (Windows Functions, Joins & Subqueries)
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In the second technical round interview asked me about advanced sql topics, theory questions and two coding questions in joins and window functions.

Q1. Tell me about your projects?
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Q2. How do you approach the project if you are using logistic regression model?
Ans. 
Approach involves data preprocessing, model training, evaluation, and interpretation.
• Perform data preprocessing such as handling missing values, encoding categorical variables, and scaling features.

• Split the data into training and testing sets.

• Train the logistic regression model on the training data.

• Evaluate the model using metrics like accuracy, precision, recall, and F1 score.

• Interpret the model coefficients to under...read more
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Q1. What are you future goals?
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Q2. What would you do if your interested field doesnt have any work in the company?
Ans. 
I would seek opportunities to apply my skills in related fields within the company.
• Explore other departments or teams within the company that may have projects related to my field of interest

• Offer to collaborate with colleagues in different departments to bring a new perspective to their projects

• Seek out professional development opportunities to expand my skills and knowledge in related areas
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It was an online assessment. Some coding questions. Some cs fundamental mcqs. SQL query, Rest Api question.

An assignment to create a game using nodejs/ go lang/ java.

Q1. Discussion related to Assignment. Told some changes and told to add some more functionalities.
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Q2. Some APIS were given. It was case study. You had to show the dishes to a customer according to his preferences.
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Q1. Basic Excel Questions
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Q2. Medium and Basic SQL Questions
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Q3. Resume based Question
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Q4. Case Study Questions
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Q5. Questions on Project
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