Node.js Interview: 36 Best Questions to Ask

Before, I have presented the critical knowledge necessary for React-centric programming. On its basis, you can easily create a proper interview and find a professional to provide Node.js development services. I also conduct other types of interviews. Above all, they include Node.js. I want to assist you with finding great people to fill positions in your business. So, here come the questions/answers prepared for detecting experienced Node.js experts.

Generally, I have several major segments. A strong Node.js programmer must know many things beyond their field. Hence, the main themes include the following elements:

• General programming/coding;
• Control over JavaScript;
• Management of the Databases;
• Node.js abilities;
• Transfer of information within a network
• Safety and overall security;
• Skills of testing the resulting code.

The overall structure will be simple. Above all, the importance of a certain field will receive analysis. After that, the readers will get essential issues for structuring a strong interview.

General programming/coding

One of the things you must understand regarding Node.js is its interconnected nature. When a programmer uses the language, they will eventually work with other important pieces of software. General coding knowledge is crucial considering these factors. The necessity of programming in other languages or using some complex architectures would not bewilder a good Node.js developer.

Question/Task 1. List the strengths and problems monolithic and microservice architectures have today.

The primary type of architecture usually requires less time for support. The approach is clearer than the microservice method, which is known for issues with scope increases, maintenance, and long-term servicing.

Generally, microservice frameworks have tighter and more complex structures. They will undoubtedly be difficult to incorporate into work. Microservice-based applications ultimately perform worse than monolithic ones. Still, there is also one strength to consider.

Microservice-centric methods require less time for scaling and do not need much resources for proper development.

Question 2. Could you talk about the sorting approaches you use? What differences exist?

The number of algorithms is rather large today. You can sort by selection and via bubbles. Quick and merge-centric approaches are also available to programmers. I believe all principles have their strengths. An expert must decide which one to use personally. For example, use a selection approach if you need to find some smallest (in terms of value) segment. Do you strive to do something about neighboring sectors? Use the bubble-centric method here.

Question/task 3. Describe what you know about the sophistication of a sorting approach. Do you have knowledge of making them efficient?

Usually, sorting algorithms depend on two things for complexity: time and memory they take. We signify the complexity of sorting as O. Three types of it exist:

• O(n): sophistication is on the linear level (approach aimed at finding maximal segments);
• O(log n): complexity becomes logarithmic (all types of binary-centric analysis);
• O(n^2): complexity is square (classification by insertion).

Question 4. Contrast horizontal-focused and vertical-centric scaling approach: how they diverge?

When you use vertical scaling, you provide energy for more existing machines (for example, if you install a new SSD). The horizontal approach typically means an expansion through new devices.

Question 5. Talk about the SOLDI, ACID, and CAP structures. Have you utilized anything like that for your projects?

SOLID means single responsibility, open-closed. CAP is a theorem. Some also know it as the Brewer approach. It claims that information distributed along several types of storage can only achieve two out of the three key demands simultaneously. They include partition tolerance, availability/accessibility, and consistency. Lastly, ACID is short-term for atomicity, consistency, isolation, and durability. All of these elements appear to be crucial in the proper management of databases. Regarding experience, a typical candidate must have at least certain knowledge of applying the models in real-life work.

Control Over JavaScript

Node.js opens the possibility of developing the internal side of various software through JavaScript. If you do not know the latter coding approach, you will fail to write a proper back end in many cases. Thus, a good interview must check whether a candidate at least knows fundamental parts of the language.

Question 6. How do we understand "this" keyword? What uses are available for it? Contrast the method with context-based approaches.

JavaScript uses the "this" word to highlight an element that proves to be part of an object. For example, the "this" keyword placed in a method signifies local-centric elements. If placed on its own within a certain function, it means a universal or global factor. The contrast of context and "this" is simple. Context concentrates on objects placed within a performed segment of code. "This" is about elements where a certain function undergoes a performance process.

Question 7. Can one transform "const-marked" objects? List the ways of preventing changes if the response is positive?

Certainly, one can easily change numerical information in any object despite it manifesting as "const." The main way to avoid this problem is to put it into stasis (the key coding formula here is Object.freeze())

Question 8. How do we define scope? What relation does it have to JavaScript?

Scope helps find whether various variables are available to a developer. Scopes are global, available in the whole program, and local, being usable only within some element of code.

Question 9. Define the bind(), call(), and apply() approaches. Could you explain the divergences between call() and apply()? Is it possible to create a personalized version of bind() through apply()?

Above all, we have to define the key terms in the presented case. call(), as its name implies, calls for a function and lets arguments go through it one after another. apply() does the same thing but pushes code via an array-centric approach. Lastly, bind() helps reverse internal elements and ensure they will work in a correct situation.

Regarding the instances of use, they typically rely on the abilities of an average programmer. There are many solutions available to developers. I believe a good candidate must know at least one to pass an interview.

Question 10. Arrow and regular functions: could you contrast them?

Arrow functions are a new thing. The developers have introduced them rather recently to help optimize coding. Regular functions are constructible and callable. Contrary to that, arrow approaches are only callable. You can't create them via a function expression method. Arrow approaches also do not use "this" keywords; they can't utilize argument-centric objects.

Management of the Databases

All developers of internal (back end) processes must encounter databases. After all, the typical back end helps manage the information interaction of a database and an average browser. Thus, once you have ensured the skills concerning the central back end platform, JavaScript, one should look at databases.

Question 11. Contrast relational and non-relational databases: how to use them?

If you want to conserve data in tables (for instance, via MySQL), the greatest idea includes relational approaches. Need JSON documents? Use non-relational frameworks (for example, MongoDB). The primary database type is crucial for ensuring the efficiency of dynamic query methods. Contrary to that, non-relational approaches seem to be central to managing large-scale projects.

Question 12. What approaches to database normalization exist? Describe the optimal level for normalizing an average database.

Several major ways of normalizing a database exist, 1NF (normal form), 2NF, and 3NF. The primary stages hold information in tables of relational types; data is separate, and no repetitions between different groups exist. The second database stage typically involves all preceding elements but groups its columns along some main key. The third stage once again features all previous characteristics. Simultaneously, it adds a new important element: all information must be independent of primary keys regarding transitive fashion.

Other levels also exist within modern database management. Some databases, for example, have a so-called BCNF or 3.5 level (Boyce-Codd). This approach demands the presence of preceding features and a hyper/super key (such as X) in all dependencies between, for instance, objects X and Y. Lastly, the fourth and fifth groups also exist. Like preceding stages, they build upon previous approaches. The fourth level features multivalued dependencies within it. Lastly, the fifth phase can't separate itself via several minuscule table-oriented objects. There must be no decomposition.

Concerning the second part of the question, no correct answer exists. Different situations, most obviously, require diverging approaches. A person can't limit themself to the singular method.

Question 13. Describe the JOINs in SQL and their variety. How to spot divergences in them?

Currently, SQL has five instances of JOINs. They include cross, full, right, left, and inner approaches. I like using an example of intersecting circles (X and Y) for the phenomenon.

Let's imagine that circles correspond to tables and intersecting spaces feature similar information.

Right JOIN includes all information from circle Y: in short, it has all data from table Y without references to table X. Left JOIN is a similar thing but for area X. Full JOIN, as one can already guess, involves all data. Inner JOIN is about the intersecting areas. Lastly, cross JOIN deals with some product (usually, cartesian) stemming from an interconnection between two tables.

Question 14. Explain the functionality of indexes. What do they stand for?

Using indexes, a person can categorize information within a database. In this regard, the analyzed element is nothing but a set of numbers. A typical index features two things. Firstly, it has a field value. Secondly, it uses a pointer to highlight some database elements. On this basis, one can sort various indexes. This approach is highly useful because it helps decrease the amount of time for search. After all, an index points to the area necessary for database analysis.

Question 15. What do "atomicity" and "aggregation" stand for?

If you need to make sure all actions within some transaction work simultaneously, the good idea is to go for atomicity. Typically, if a transaction can't reach a finale, the database tools will revert all key actions.

As for the aggregations, they represent some relationships that feature an expression through a multitude of entities and the interconnection between them.

Question 16. Could you explain ORM?

ORM is easy to define: it describes object-relational mapping. You can use this approach to transition data based on proper object-centric coding while having incompatible systems.

Question 17. What relation types exist in the current conditions?

The following approaches to relations exist currently:

• many-to-many framework: information from a table can connect with all records from other tables;
• one-to-one approach: one record from a singular table can connect with one piece of information from another;
• one-to-many approach: one piece of information from a table can connect to all types (in terms of number) of records from other available tables.

Node.js Abilities

Want to hire a Node.js developer? Make sure they know Node.js programming. It is simple.

Question 18. What is the overall approach to asynchronicity in the programming language?

Asynchronous operations typically occur when a certain action can start before the completion of others. The approach works through the non-blocking input/output method based on events in Node.js.

Question 19. Explain the nature of an event loop. What is the way it works in Node.js?

This element typically analyzes call-related issues (for instance, stacks and queues). For example, let's imagine an empty call stack. The event loop takes an event from a queue and pushes it into a call stack for the performance process. Every cycle of this event loop is a so-called tick. All events, at the same time, are callbacks to varying functions.

Six phases are present in the average event loop. Firstly, the object undergoes a poll. Secondly, a check befalls them. Then, close callbacks occur in one form or another. A set of timers appears for the connections. The last phases include input/output callbacks and the transition to idleness and constant preparation.

Question 20. Explain the stream types in Node.js. What differences do they have?

Node.js has five types of streams. Firstly, readable types help abstract information from the place data originates. Secondly, writable streams are the same thing as the preceding approach, but they abstract data from the place to which information goes. Thirdly, duplex streams can engage in both read and write operations. Fourthly, the transform method is also read/write; it can, at the same time, modify the information during the processing. Lastly, pass-through methods are simplified versions of the transform approach (based on passing information bytes). They aren’t practical in real-life scenarios. The best idea is to use the approach for tests of various kinds.

Question 21. Define the process.nextTick(), setImmediate(), and setTimeout(() => {}, 0). What order should we use to start them?

• The first approach prevents the function from starting before the new cycle of an event loop;
• The second method helps begin a scenario after the completion of an existing poll stage.
• The last approach sets up the launch for some scenarios based on the minimal time interval created by a developer.

As for the order, the one outlined in the question is correct. There is no need to introduce any changes.

Question 22. What does child_pocess stand for, and how can we use them?

child_process is a function capable of, as its name suggests, helping utilize different capabilities of an operating system through a child process.

As for the uses of the approach, many answers exist. The more experienced a developer is, the more they know about this element.

Question 23. How to prevent the blocking of input/output operations in Node.js?

The event-based approach of Node.js helps solve the presented phenomenon. The use of event loops rather than threads in the programming language is also an essential factor.

Transfer of information within a network

One of the things all developers have to work with includes data transfer APIs. To prevent big security problems, a person has to understand how networks work in general.

Question 24. What is the overall functioning of the HTTPS? What SSL certificates can we use?

HTTPS is a secure version of the HTTP protocol. The aforementioned SSL stands for S in the HTTPS abbreviation. It typically represents a security key that helps establish a safe connection between servers and browsers. Ultimately, three types of SSL certificates exist by validation: domain, organization, and extension-centric ones.

Question 25. What is REST and its main principles?

REST includes the following elements:

• Contract-centric methodology and unified approach regarding uniform resources are a must;
• Architecture has to be layered;
• No concentration on states (statelessness) is essential;
• A clear client-server framework is crucial;
• Developers must use caching for managing data.

Question 26. What is SOAP? Contrast it with REST.

SOAP is a Simple Object Access Protocol. REST involves Representational State Transfer. The main difference between them is in the nature of the platforms. SOAP is protocol-centric; REST is an approach to building architecture.

Another difference exists in the availability of tools. SOAP works with XML alone. Contrary to that, REST is perfect for plain text, HTML, JSON, and, once again, XML. Often, REST can openly incorporate the SOAP methods. Lastly, bandwidth is also a source of major differences. SOAP typically requires more of it than REST.

Question 27. What do you know about platforms such as RabbitMQ (message brokers)? Why should we use them?

Methods like this help transition data from a sender and their protocols to the receiver and, once again, their protocols. The technology gives a chance for various programs to interconnect. Ultimately, we use message brokers to help microservices. Let's imagine one of them stops working. We can use a message broker to store the data until the technology restores itself. As a result, the number of data losses decreases rather significantly.

Question 28. Could you explain the concept of long polling?

Long polling is a simple process. Its ideal is to maintain a client connection until new data appears within a server. In the past, web experts had a problem: clients were the main initiators of all data requests. Long polling allows servers to prepare data without referencing the clients. It is important for proper autonomy regarding functioning.

Safety and overall security

This one is obvious. We live in a world of tremendous security threats. Thus, our goal is to ensure the data of the customers are as safe as possible. A good Node.js developer must know the key methods of attack.

Question 29. Explain SQL injections. What ways to prevent them exist?

SQL injections involve attacks on databases. Attackers insert malignant code through web-centric inputs. The best way to prevent such assaults is not to write dynamic queries of any kind. Experts should also isolate user inputs in one way or another.

Question 30. What about a timing attack? How should we handle them?

We can find security gaps by studying the responses to different requests. There is a simple way to prevent them: string comparison mustn't rely on their size. Another crucial thing is to analyze all string values before executing code.

Question 31. What should we do with the broken access control?

Broken access control occurs due to some errors with security optimization. Sometimes, outside users and, of course, attackers can enter closed parts of a website.

Avoiding the issue is rather simple, however. You should concentrate on the following things:

• Install checks for access: some password or other form of authentication can help prevent entry into closed parts of a website.
• Don't rely on ID;
• Create clear file permissions (secure documents must have anti-read/write protection);
• Remove any vital information from cache: attackers should have no chance to find data about web pages through saved pages.

Question/Task 32. Explain server-centric XSS.

XSS or cross-site scripting includes some form of malignant code or other negative inputs in the HTML output generated by server data. Usually, hackers use requests of different kinds to achieve this type of attack. Encoding some sensitive information is essential for preventing the problems in question.

Question 33. Could you explain the same-origin policy approach?

This phenomenon is an important approach capable of preventing contact between information with one source and data of a different origin. You can use the method to stop leaks of important information in one way or another.

Skills of testing the resulting code

We, of course, have QA teams in our companies. This fact doesn't excuse the lack of initial testing. A developer knows his programs best. Thus, they should be at the forefront of checking validity.

Question 34. What libraries are crucial for the existing approaches to testing? Why do we write tests at all?

I recommend using libraries such as Mocha/Chai and Jest/Jasmine.

The second part of the question is philosophical. One can find out the mindset of a candidate through this method.

Question 35. Explain mocks and stubs. What's the need for using realistic information?

The objects are approximations: they help emulate real-life project-related activities. Stubs signify data one can use for calls. As for the mocks, they involve various register calls crucial for the verification of key actions.

The data has to be realistic to ensure more or less genuine conditions appear. What is the point of testing if it is distant from reality?

Question 36. For a CI, is it reasonable to test all pull requests?

Here, we also talk about philosophy. My answer is simple: tests are crucial during the presentation of some key features. At the same time, it isn't a good idea to go for this process during active development. Regrettably, the approach takes too much time.

Conclusion

I believe the article will be of great use to all types of readers. Developers can use it to prepare for interviews. Employers will benefit from using the data to structure the job application process.

If you are still confused, you can always contact us https://keenethics.com/. We know how to assist you with questions and even are capable of helping find Node.js developers.