Query Optimization Interview Questions

16 real Query Optimization questions asked in live technical interviews — each with a model answer. Updated weekly.

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These Query Optimization 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.

How do you optimize slow queries that are taking a long time?🟡 Medium · Conceptual · Asked 1×How do you optimize queries in PostgreSQL?🟡 Medium · Conceptual · Asked 1×If I tell you that this query will take a lot of time, how would you optimize it? What steps would you take to improve its performance?🟡 Medium · Conceptual · Asked 1×What method would you use to optimize this query? You can choose any method you want, such as adding indexes or rewriting the query.🟡 Medium · Conceptual · Asked 1×Suppose you're given a dataset with 10 million rows and you need to perform a complex query that involves aggregating data from multiple tables. How would you optimize the query for better performance?🟡 Medium · Conceptual · Asked 1×Suppose you have a dataset with 10 million rows and need to run a complex query that aggregates data from multiple tables. How would you optimize the query for better performance?🟡 Medium · Conceptual · Asked 1×How can a slow query be optimized to fetch results fast?🟡 Medium · Conceptual · Asked 1×How do you optimize a data model to improve query performance, for example, reducing a query that currently takes minutes to run?🟡 Medium · Conceptual · Asked 1×Can you rewrite the query?🟡 Medium · Coding · Asked 1×Can you rewrite the query in a more optimized way, removing any inefficient correlated subqueries?🟡 Medium · Coding · Asked 1×Can you walk through a complex SQL query you have written recently in your career?🟡 Medium · Conceptual · Asked 1×What are query optimization techniques?🟡 Medium · Conceptual · Asked 1×How do you optimize a slow-running query?🟡 Medium · Conceptual · Asked 1×When writing queries, what sort key strategy would you use?🟡 Medium · Conceptual · Asked 1×We have a query that normally runs for 4 minutes but is currently running for 30 minutes. What would you do?🟡 Medium · Debugging · 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×

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