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Interview practice

.NET Developer

5–8 years · Senior — C# · ASP.NET Core · Entity Framework · SQL Server · LINQ · Azure

0–2 years 2–5 years 5–8 years 8+ years
technical Entity Framework 1 of 6
A migration introduced a new table, and now change tracking is causing significant performance degradation. What do you investigate, and how do you respond?
What a strong answer covers

Examines the size of the tracked entities; checks if tracking should be disabled for read-only queries; considers using AsNoTracking for performance; reviews the number of relationships and navigation properties; evaluates the impact of lazy loading on performance.

The follow-up you would get

What are the trade-offs of using AsNoTracking?

Could you have answered that?
technical Deployment 2 of 6
After deploying a new version of an application to Azure, users report a significant increase in response times. What steps do you take to troubleshoot the issue?
What a strong answer covers

Checks Azure Application Insights for performance metrics; reviews the deployment logs for errors; examines the scaling settings and resource usage; assesses the impact of new dependencies or configuration changes; compares the current and previous versions for differences.

The follow-up you would get

What Azure services can you leverage for better performance monitoring?

Could you have answered that?
technical Async and Concurrency 3 of 6
An API endpoint that previously handled 100 concurrent requests now fails with timeouts when load increases to 500. What steps do you take to identify and resolve this issue?
What a strong answer covers

Checks for thread pool exhaustion; reviews async/await usage for proper application; examines task scheduling and any blocking calls; considers implementing throttling or circuit breaker patterns; evaluates service dependencies and their performance under load.

The follow-up you would get

What specific patterns can you implement to improve scalability?

Could you have answered that?
technical System Design 4 of 6
An application that processes user transactions has experienced data inconsistencies with a spike in users. How do you design the system to handle this issue?
What a strong answer covers

Identifies the need for eventual consistency; designs with CQRS (Command Query Responsibility Segregation) pattern; considers using distributed transactions or event sourcing; implements a retry mechanism for failed transactions; assesses data partitioning strategies for scalability.

The follow-up you would get

How do you ensure that the system remains performant under high load?

Could you have answered that?
scenario Design and scaling 5 of 6
You are tasked with designing a new microservice that must handle variable loads and ensure high availability. What are your first steps?
What a strong answer covers

Defines clear service boundaries and responsibilities; chooses a suitable API protocol (REST or gRPC); implements rate limiting and circuit breakers; designs for eventual consistency and data replication; plans for horizontal scaling using container orchestration; evaluates cloud service options for resilience.

The follow-up you would get

What considerations do you have for handling data migrations in this microservice design?

Could you have answered that?
scenario Ownership of incidents 6 of 6
A production incident arises where users are unable to log in due to a misconfigured authentication service. How do you manage the incident and communicate with stakeholders?
What a strong answer covers

Immediately assesses the service status and error logs; rolls back the recent configuration change if necessary; establishes a communication plan for updates; creates a temporary workaround for affected users; documents the incident for post-mortem analysis; identifies root cause and plans for prevention.

The follow-up you would get

After resolving the incident, how do you ensure similar issues do not occur in the future?

Could you have answered that?
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