Nail the microservices interview: Let’s talk about .NET

Imagine that you have a very complex system in your hand, which is broken down into several microservices to run. The code I write is okay, but every time I go for a job interview, a question arises - how do I ask to know if the other person really understands it? Anyone can memorize those theoretical concepts, but when it comes to the specific implementation in .NET, the details become blurry.

We have talked to many teams and found that everyone has the same headaches. Some people ask too superficially and just ask "What are microservices?"; some people dig too deep and are entangled in a certain unpopular configuration item. The interviewer may have just started working on it himself, and after asking many questions, he still feels like he doesn’t know the ropes.

In fact, interviewing is a bit like debugging code. You need to know where the critical breakpoints are.

From theory to implementation: What exactly are you asking in .NET?

Microservices sound lofty, but when it comes to .NET projects, it is just a series of specific choices and practical operations. For example, for containerization, do you use Docker or directly Kubernetes? How to design API gateway? Do I need to ride it myself if I find the service? Behind these questions lies a deep understanding of architecture.

There is a common misunderstanding: many people know the technology stack by heart, but they can’t explain why they chose this one instead of that one. In the .NET ecosystem, there are a lot of tools and frameworks, and every choice has its price. During the interview, we want to hear the thinking behind it instead of listing nouns.

"If communication between services suddenly slows down, where would you start?" There is no standard answer to this question, but it can tell whether a person has really done a lot of work or just read a few blogs.

How do you find out your true skills?

Don’t just focus on concepts. Going directly to the scenario: "Suppose you now have an order service and an inventory service, and inventory is deducted when the order is created. How do you ensure that the data will not be messed up?"

At this point, the answer might involve message queues, distributed transactions, or eventually consistent designs. In .NET, you may use MassTransit or NServiceBus, or you may use RabbitMQ directly. But the point is not the tool name, but the choice - why is it used this way? What's the cost?

Talk about the experience of failure. Who hasn’t stepped on a pitfall on the road to microservices? Network timeouts, confusing configuration management, inadequate monitoring... Listen to what specific problems the other party encountered and how they solved them. This is much more useful than a perfect theory.

The .NET environment has a characteristic: it is both traditional and modern. Many teams were separated from old single systems and carry heavy historical baggage. Good interview questions should reveal the other person's ability to handle this complexity.

Keep it simple, but not too simple

When designing problems, it is easy to go to two extremes: either too abstract or too trivial. Good interview questions should be like writing code, with clear modules but room for expansion.

For example, when asking about logs and monitoring, you can say: "Microservices are scattered, and logs are also scattered. How do you string together clues?" This may lead to the ELK stack, Seq, or directly to Azure Application Insights. But more deeply, how do you define log levels? How to avoid having too many logs and not being able to find the key points?

Or ask security: "With so many services, how to manage authentication?" At this time, we may talk about OAuth2, JWT, or API key rotation. In .NET, IdentityServer is a common choice, but it is not the only answer.

The key is not whether the other party knows a certain tool, but whether he understands the nature of the problem.

our own experience

To be honest, we didn’t know how to ask from the beginning. At the very beginning, the list of questions looked like a textbook table of contents, and I still felt unsure after the interview.

Later, we gradually understood that the interview is not an exam, but a conversation. You want to understand how the other person thinks, and the other person also feels the technical atmosphere of your team. So now, we prefer to come up with a simplified real-life scenario and discuss possible solutions together. What can be exposed in this process is far more than the standard answer.

The .NET microservices ecosystem is constantly changing, and new tools and models are constantly emerging. You have to adapt to the interview questions, and you can't always stick to the same routine as a few years ago. But the core things have not changed: solid programming foundation, clear design thinking, and willingness to solve practical problems.

A few words of small talk

In the final analysis, interviews are about finding people with whom you can solve problems together. The microservice architecture itself is complex enough, and what the team needs is a partner who can simplify the complex.

So, when preparing for an interview next time, think less about "standard questions" and more about "what troubles have we actually encountered." Talk about those real little struggles and tangles, and the answers often lie there.

Technical details will become obsolete, but the way you think about them will not. Finding someone you can think of going with is probably the most important thing to do in an interview.

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