Top 50 Performance Optimization Interview Questions 🚀

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Introduction

Performance optimization is a critical skill for developers, database administrators, and system architects. Whether working with .NET, SQL, EF Core, Dapper, or designing large-scale systems, interviewers often test candidates on their ability to identify bottlenecks and implement efficient solutions. This blog organizes the Top 50 Performance Optimization Interview Questions into structured sections for easy preparation.

1. .NET Performance

  1. How do you improve performance in .NET applications?

  2. What is garbage collection and how does it affect performance?

  3. How do you reduce memory leaks in .NET?

  4. Difference between synchronous and asynchronous programming in terms of performance?

  5. How do you use caching in .NET applications?

  6. What is the impact of boxing/unboxing on performance?

  7. How do you optimize string operations in .NET?

  8. How do you use parallel programming for performance gains?

  9. What is the difference between Task and Thread?

  10. How do you profile a .NET application?

2. SQL Performance

  1. How do you optimize SQL queries?

  2. What is indexing and how does it improve performance?

  3. Difference between clustered and non-clustered indexes?

  4. How do you identify slow queries in SQL Server?

  5. What is query execution plan?

  6. How do you use normalization vs denormalization for performance?

  7. How do you optimize joins in SQL?

  8. What is the impact of subqueries on performance?

  9. How do you use partitioning in SQL databases?

  10. How do you handle deadlocks in SQL Server?

3. EF Core Performance

  1. How do you optimize queries in EF Core?

  2. What is AsNoTracking and when should you use it?

  3. How do you reduce round-trips to the database in EF Core?

  4. What is query splitting in EF Core?

  5. How do you use compiled queries in EF Core?

  6. How do you handle lazy loading vs eager loading?

  7. How do you optimize migrations in EF Core?

  8. How do you use batch updates in EF Core?

  9. How do you profile EF Core queries?

  10. How do you handle concurrency in EF Core?

4. Dapper Performance

  1. Why is Dapper considered faster than EF Core?

  2. How do you optimize queries in Dapper?

  3. What is buffered vs unbuffered query in Dapper?

  4. How do you use QueryMultiple in Dapper?

  5. How do you batch insert records with Dapper?

  6. How do you handle transactions in Dapper?

  7. How do you optimize mapping in Dapper?

  8. How do you use asynchronous queries in Dapper?

  9. How do you profile queries executed via Dapper?

  10. How do you integrate caching with Dapper?

5. System Design Performance

  1. How do you design scalable systems?

  2. What is load balancing and how does it improve performance?

  3. How do you use caching in distributed systems?

  4. Difference between vertical scaling and horizontal scaling?

  5. How do you design systems for high availability?

  6. What is CDN and how does it improve performance?

  7. How do you handle database sharding?

  8. How do you design systems for fault tolerance?

  9. How do you optimize API performance?

  10. What are best practices for performance in microservices architecture?

Conclusion

These 50 questions cover the breadth of performance optimization knowledge expected from experienced developers and architects. From .NET and SQL to EF Core, Dapper, and system design, this list serves as a comprehensive guide for interview preparation. By mastering these topics and preparing answers with real-world examples, you’ll be ready to tackle interviews confidently.

This was part of Interview Preparation With Bipin — Let’s Crack It!

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