Performance Interview Questions

19 real Performance questions asked in live technical interviews — each with a model answer. Updated weekly.

🎤 Auto-captured by Assisting AI during live interviews

These Performance interview questions were captured from real interviews by candidates using Assisting AI. Each links to a full model answer. For real-time help during your own interview, get Assisting AI from ₹500/day.

Using the Parquet file format, queries are fast. What optimizations are done using Parquet?🟢 Easy · Conceptual · Asked 3×Why are wide transformations costly?🟡 Medium · Conceptual · Asked 1×How can a slow query be optimized to fetch results fast?🟡 Medium · Conceptual · Asked 1×How do you handle performance when processing a large number of records?🟡 Medium · Conceptual · Asked 1×Let's say we are doing data backup on S3 storage and it's taking a lot of time. How would you mitigate this issue? What approaches would you have?🟡 Medium · Conceptual · Asked 1×Scenario: we have a massive sales table and a smaller product table. The join is taking too long. What would you do?🟡 Medium · Debugging · Asked 1×Let's say the data is stored on a host server and is a little large. Will that pose any issue if we expose it via a REST API? If so, what solution would you propose?🟡 Medium · Conceptual · Asked 1×What specific indexes would you create for an optimized version to support those joins and filters?🟡 Medium · Conceptual · Asked 1×Can you tell how to optimize Spark jobs for streaming data?🟡 Medium · Conceptual · Asked 1×If we have a huge table in Amazon Redshift, what options would you consider to optimize its performance?🟡 Medium · Conceptual · Asked 1×The table is queried by ID, but the ID is modified frequently.🟡 Medium · Conceptual · Asked 1×We are processing a 1PB dataset on an MR cluster. The job is a join between a large sales dataset and a medium‑sized stores dataset. The job consistently crashes without a memory issue. Why do you think the executioner is failing?🔴 Hard · Debugging · Asked 1×A pipeline ingests data into an ISO table every hour. Over six months, query performance has dropped and S3 storage cost has spiked due to millions of tiny metadata files. What approach would reduce cost and improve pipeline performance?🔴 Hard · System Design · Asked 1×Suppose a query was running, and suddenly it starts taking a long time to execute. What could have gone wrong with the query source?🟡 Medium · Debugging · Asked 1×Why is Spark faster than normal Python computations?🟡 Medium · Conceptual · Asked 1×Why do we need to take timing into account?🟢 Easy · Conceptual · Asked 1×If we are going to display 10,000 records at a time, what would we do?🟡 Medium · Conceptual · Asked 1×How can you efficiently grow a particular grid in a React application?🟡 Medium · Conceptual · Asked 1×Suppose you need to display under 10,000 rows efficiently; what ways can you achieve this?🟡 Medium · Conceptual · Asked 1×

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