Mastering the Senior C# Engineer Interview
#csharp#softwaredevelopment#learning#dotnet
Odumosu Matthew

Odumosu Matthew @iamcymentho

About: Experienced software engineer in C# - .NET and JAVA - SpringBoot, with a financial sector background. Passionate about technical writing and sharing project experiences. Eager to learn and grow

Location:
Lagos, Nigeria
Joined:
Jul 26, 2023

Mastering the Senior C# Engineer Interview

Publish Date: Feb 10
142 10

This is a solid approach—testing a senior C# engineer’s hands-on experience through real-world scenarios. Below is a comprehensive list of
at least 30 in-depth senior-level interview questions with detailed explanations and answers. These questions focus on transaction handling, distributed systems, performance optimization, security, and system design—all crucial in a financial organization and industry as a whole.

1) TRANSACTION FAILURE AND RETRY MECHANISMS
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transaction failure

ANSWER
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The best approach is to use a retry mechanism with idempotency. This can be done via:

- Implementing a retry policy using Polly:

polly

  • Retries up to 3 times before failing.

  • Uses exponential backoff to prevent overload.

- Using a background job queue (Hangfire, Quartz.NET, or MassTransit):

bacgroundjob

- Database-based tracking:

database

2. Deadlocks in SQL Transactions
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deadlocks

ANSWER
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- Use a consistent ordering of operations:

sql

  • Always debit before credit to prevent deadlocks.

- Lower the lock scope:

sql

- Retry logic in case of deadlock:

polly

3. Handling High-Volume Concurrent Transactions
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concurrency

Answer:
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payment

4. Preventing Double-Spending in Distributed Transactions
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transactions

Answer:
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transactions

5. Optimizing Database Queries for Real-Time Processing
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database

Answer:
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- Use database indexing:

indexing

- Use pagination for large queries:

pagination

6. Securing API Requests & Authentication
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Authentication

Answer:
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Authentication

7. Handling Long-Running Processes in .NET
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Processes

Answer:
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Processes

8. Handling Race Conditions in Multi-Threaded Environments
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race condition

Answer
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- Use database transactions with row-level locks:

database

9. Logging & Monitoring in Production
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logging

Answer:
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logging

10. Handling API Failures in a Microservices Architecture
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Microservices

Answer:
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API

11. Handling Concurrency in a Banking System
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Concurrency

Answer:
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Concurrency

12. Preventing API Rate Abuse
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API Rate

Answer:
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API Rate

13. Ensuring Data Consistency Across Microservices
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Microservices

Answer:
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Microservices

14. Secure Storage of Sensitive User Data
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user data

Answer
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user data

15. Designing a Real-Time Fraud Detection System
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fraud detection

Answer:
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fraud detection

16. Avoiding Memory Leaks in Long-Running Services
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fraud detection

Answer:
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fraud detection

17. Designing a Scalable Logging System
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logging

Answer
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logging

18. Handling Time Zones in a Global Financial System
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time zones

Answer
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time zones

19. Scaling a .NET API to Handle Millions of Requests
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API Requests

Answer:
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API Requests

20. Optimizing SQL Queries for Large Data Processing
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SQL Queries

Answer:
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SQL Queries

21. Handling Large Reports in a Financial System
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financial system

Answer
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financial system

22.  Eventual Consistency in Distributed Systems
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distributed systems

Answer
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distributed systems

23.  Implementing Circuit Breakers in Microservices
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Circuit Breakers

Answer
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Circuit Breakers

24.  Preventing Unauthorized Transactions
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Unauthorized

Answer:
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Unauthorized

25. Caching Strategies for Real-Time Banking Data
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caching

Answer:
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caching

26. Secure Storage of API Keys
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API Keys

Answer
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API Keys

27. WebSockets vs SignalR for Real-Time Updates
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WebSockets

Answer
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WebSockets

28. Handling Mass Fund Transfers Efficiently
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Transfers

Answer:
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Transfers

29. Role-Based Access Control (RBAC) in a Banking App
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Role-Based Access Control

Answer:
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Role-Based Access Control

30.  Building an Event-Driven Architecture for Bank Notifications
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Event-Driven Architecture

Answer:
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Event-Driven Architecture

31. Using CQRS with Separate Read and Write Models in a Financial App
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CQRS

Answer:
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CQRS

LinkedIn Account : LinkedIn
Twitter Account: Twitter
Credit: Graphics sourced from CodeQuotient

Comments 10 total

  • Spyros Ponaris
    Spyros PonarisFeb 10, 2025

    Thanks for sharing !!! Some answers were blank. Will be nice to add some implementation as well .

    • Odumosu Matthew
      Odumosu MatthewFeb 11, 2025

      Thank you for your feedback! The answers should now be fully displayed. I’ll update it with some implementations soon as well.

  • Bobby Bridgeman
    Bobby BridgemanFeb 11, 2025

    Should be titled senior database engineer with the amount of db related questions!

    • Odumosu Matthew
      Odumosu MatthewFeb 11, 2025

      Haha, you’re right! Seems like the database questions definitely took the spotlight.

  • Lang Flow
    Lang FlowFeb 11, 2025

    Mastering the interview for a Senior C# Engineer is not a walk in the park, but with proper preparation, it's definitely doable! Focusing on advanced concepts in C#, system design, and problem-solving really gives one the edge. Good luck to all those preparing; just be confident and keep practicing!

  • Dinesh Dixit(Mechatron)
    Dinesh Dixit(Mechatron)Feb 11, 2025

    Thanks for sharing. It's helpful.

    • Michelangelo Partipilo
      Michelangelo PartipiloFeb 12, 2025

      The images were also very impractical to read on a mobile phone. I had to zoom and scroll each image to read. It quickly became frustrating.
      I did love the content though. Lots of pearls of wisdom.

  • CitronBrick
    CitronBrickFeb 11, 2025

    Please prefer text to images for the answers. It's more accessible.
    Or add alt messages.

  • Serg Dev
    Serg DevFeb 14, 2025

    Definitely amazing article). I would add something about the event sourcing)

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