Complete hiring guide for Node.js: Interview questions, where to source devs & more

Looking for a great Node.js developer for your project that can provide you with a speedy, lightweight and scalable backend solution? Look no further, ‘cause this hiring guide for Node developers will answer all your questions.

Stefanija Tenekedjieva

Stefanija Tenekedjieva

Alexandre Brandizzi

Alexandre Brandizzi

Complete hiring guide for Node.js: Interview questions, where to source devs & more

The backend solution Node.js is a runtime environment that enables JavaScript to be executed on the server.

Due to its remarkable performance, an increasing number of businesses such as Netflix, LinkedIn and PayPal are employing Node specialists.

Node is one of the most versatile backend languages on the market. A company normally requires a NodeJS developer when they work with microservices architecture or lambdas.

Aside from the global market perspective, NodeJS has been the fastest-growing technology along with the competitors, granting a huge community worldwide. Meaning, it is easy to find a Node developer to scale up your activities or keep the maintenance of your services if they are no longer evolving.

About Node developers

There are pros and cons to any technology, but Node seems to weigh down more in the former category. We talked to Fullstack Developer Alexandre Brindizzi to understand the applicability of Node.js, what exactly Node developers do and are skilled in, and why he believes it is a wise investment to hire a Node developer.

"Fast-growing tech; versatile usage with multiple Node.js frameworks granting ease of usage for developers; a big and wide community worldwide turning it very easy to find NodeJS developers to interview and possibly hire; the fact that a developer who knows Node may also know other technologies based on the JavaScript programming language, such as React or Angular, are all factors granting you someone who will give you a full-scale architecture perspective and good practices along the development."

author Alexandre Brindizzi

Not surprisingly, because of its numerous benefits, Node is the most popular and widely used for 2023, according to a Statista survey.

After this pitch, it comes as no surprise that a Node developer is very valuable to any team that operates with this technology. But, what does a Node.js developer’s work day look like? What do they do, exactly? Let’s explain it step by step.

Tasks and responsibilities

Deploying and administering network applications written in JavaScript or its derivatives, such as IcedCoffeeScript and CoffeeScript, are the responsibility of a Node.js developer. They create backend components, manage data transmission between servers and users, and link apps to external web services. They assist frontend developers as well by incorporating web-based programs.

A skilled Node.js developer will be able to transmit data in a way that is reliable, quick, and safe.

Practically said, here are some of the responsibilities they have:

  • Install and oversee each server-side network component.
  • Create UIs for customers and backend services for a plethora of company operations.
  • Write tested, reusable, and effective code to create high-performance apps.
  • Ensure top-notch central database performance and frontend request responsiveness.
  • Stay informed on developments in Node.js development and technology in general.
  • With frontend developers, collaborate on integrating components.
  • Enforce appropriate safety procedures, data security safeguards, and storage options.
  • Conduct tests to address flaws and offer technical assistance.
  • Describe Node.js operations, such as database schemas.
  • Advise, suggest and put into practice process and technology changes.

Expertise and niches

When asked if Node developers typically specialize in a particular niche, or if they can work in any field a software engineer might find themselves working in, Alexandre replies:

“It depends on the developer. NodeJS is nowadays used for backend services and microservices. The usage of modules in JavaScript makes it very versatile in a way you can also make it useful to lambdas for serverless methods. As previously said, a Node developer may not only be a Node developer but will probably be a multiskilled fullstack developer with React or Angular, creating full-scale applications, using Node as something complementary.”

Interviewing a Node developer

There goes a lot of thought, vetting and testing to find the right developer for a position. And since at Proxify we’re experts at this, here is what we do to achieve the best results.

Technical skills specific to Node

To start with, a good Node developer should have a broad understanding of web application principles, know at least basic algorithm complexity and understand how to write efficient code.

A Node developer should also have Unix and Windows server knowledge, preferably at least on an intermediate level.

They should understand very well how a network of containers and pods works in a Kubernetes cluster or how to dispose of that service into a Unix server to make them disposable to the web.

When it comes to cloud solutions, a Node developer should be very aware and capable of creating backend services in AWS technologies, such as deploying it to the Kubernetes cluster, creating a lambda function, and disposing of it in the API gateway, etc.

Soft skills and characteristics

Apart from the basic set of characteristics that depict any good employee (timeliness, self-organization, motivation, good teamwork and willingness to learn), and a good knowledge of English, here are some extra skills that would help a Node developer shine:

“Be a team player, among all qualities. They must see the entire scene with technical eyes, and understand how harmonic the backend they are going to work on must be, to make it not just easy for him now, but he should make it easy for anybody else about to join his team.”, says Alexandre.

He also adds that his ideal teammate should be communicative and shouldn’t make decisions alone if they’re going to impact more people.

Their architectural decisions, he adds, must follow what is more logical for long-term usage, regardless of how much effort it requires.

Interview questions

According to Fullstack Data Engineer Andrey Kolosay, here are the questions that will be most effective in assessing a Node developer’s knowledge:

  1. What is an event loop and how does it work?

Expected answer: Even though JavaScript is single-threaded, the event loop makes it feasible for Node.js to execute non-blocking I/O operations by offloading tasks to the system kernel whenever possible. The majority of contemporary kernels support several background operations since they are multi-threaded.

  1. Which web frameworks have you worked with?

Example answer: I am comfortable working with web frameworks such as Express.js,, Nest.js, Total.js, Koa.js, and others.

  1. What is the main concept of Express.js?

Expected answer: Express is a well-known, non-prescriptive web framework created in JavaScript and hosted by Node.js runtime environment. It covers setting up your development environment, carrying out typical web development and deployment chores, and some of the framework's most important advantages.

  1. What are the benefits of using streams?

Expected answer: The main reasons why you should use streams in Node are:

  • It's memory-efficient: Processing data doesn't require you to load much of it into memory.
  • It’s time-efficient: Processing data that has already been received is far quicker than waiting until the complete payload has been transferred.
  1. What are the benefits of using buffers?

Expected answer: As an alternative to an array of integers for storing raw data, Node offers the Buffer class, which corresponds to a raw memory allocation outside the V8 heap. An application can access the buffer class without importing the buffer module because it is a global class.

Alexandre, on the other hand, says that no matter the level of knowledge and years of experience, a Node developer must have the answers to the following questions.

  1. Explain why Node is a single-thread application.

Expected answer: The technology uses a single thread to run the main loop of the application and scales up based on needs, allocating threads on what is called a thread pool for asynchronous requests.

  1. What are asynchronous requests?

Expected answer: Asynchronous requests are requests that take time to be executed, and as it requires time, it cannot block the main thread with the main loop, so an extra thread in the thread pool will serve to scale up the application.

  1. What is a main loop?

Expected answer: It is where NodeJS coordinates what happens internally. The loop can never be broken, or the application will fail, so it can never stop. A request will be received, confirmed, executed and returned in that same order, always.

  1. What is Express?

Expected answer: Express is the framework globally used to create backend applications.

  1. Why is it important to work in MongoDB?

Expected answer: Because with a Mongo-Express-Node skill base, I would only require knowledge of frontend architecture to have fullstack knowledge.

Telling an expert apart

According to Alexandre, a top Node.js developer must have the maturity and understanding of how to work with strongly typed and documented code, and must know that they need to guarantee the code functionality when required, rendering unit-testing another important skill.

“They need to understand a little of server-side, and to know that Node.js is usually the best tech to deploy in a container and create multiple instances, so that service can never create conflict with other external services”, he adds.

If you are aiming into microservices, he also states, that your developer of choice should also be very mature to understand the principles of microservices, making them always independent from each other. And for some cases, they must be very aware of manual scaling with certain libraries that you can control the threads you are scaling up.

Apart from that, he should be very good with the performance, at least aware of how to work with Big O notations, understand and be very capable of explaining and working with encapsulation and may know how to design the entire backend (and what it needs) just by understanding the business.

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Why use Node.js?

Node.js is a cross-platform JavaScript runtime environment that provides an infrastructure for running JavaScript code on the backend (server-side). It’s based on Google’s V8 engine that compiles JavaScript to machine code and ensures its super-fast execution. Node.js has an event-driven architecture and leverages asynchronous programming. Those features allow Node.js servers to process huge numbers of I/O requests coming from multiple clients at an unbeatable speed.

  • How to use Node.js?

    Early-stage startups often use Node.js for fast prototyping because it allows them to write the entire project in one language. Following this approach, you can get your simple MVP built by one fullstack JavaScript developer. In production, Node.js is mostly used for building backends for web apps. You should consider using it if you’re going to build a real-time app, a messaging app, or a SPA, which all require frequent and instant updates of data. Other good Node.js use cases are scalable microservices, data-intensive IoT apps, and video streaming services.

  • What is a Node server?

    With Node.js you can build fully-fledged scalable web servers that can handle HTTP requests, WebSockets, or API requests. You can also use Node.js to build proxy servers or frontend load balancers for other servers (Apache) and use them for routing client requests.

  • Why use Node.js?

    Node.js has stood the test of time and got a rich ecosystem maintained by the JavaScript community. Node.js has proved to be a super lightweight, scalable, and fast backend tool for event-driven real-time apps, single-page apps, and microservices. The use of Node.js helps startups benefit from fstack JavaScript development, which simplifies and streamlines the app development cycle. Moreover, the list of enterprise-level apps using Node.js in production is constantly growing, which proves the health of the technology and guarantees its longevity.

  • Who uses Node.js?

    In 85% of cases, Node.js is used for the development of web apps. There are examples of successful projects that were built with Node.js from the ground up, like Trello, as well as those who moved to Node.js after trying other solutions, like LinkedIn. Among the most famous enterprise-scale Node.js app examples you’ll find Netflix, Twitter, and PayPal.

  • How secure is Node.js?

    Node.js is as secure as the code that is written using it. Most probably you’ll reuse code packages written by others and available in the Node.js ecosystem. The problem is when your project contains code from hundreds of different packages, it can be hard to spot a vulnerability. The good news is since 2018 the Node Security Platform (NSP) has been integrated directly into the npm library and runs security audits for every new module added. Anyway, for better security, make sure to use the latest maintainable versions of frameworks and modules, dive deep into the code package dependencies, and study the licensing information carefully. To mitigate the risk of attacks, hire experienced Node.js developers whose code is not vulnerable to the most common attacking techniques, such as man-in-the-middle, code injection, Advanced Persistent Threat, Cross-Site Scripting, Cross-Site Forgery Requests, and others.

  • What is Node.js not good for?

    Being a single-threaded runtime environment, Node.js is not suitable for the execution of CPU-intensive tasks. As all incoming requests are processed one by one, a heavy-computation task can block the main thread from processing all the subsequent requests. To cope with this drawback, Node.js offers a Worker Pool that summons a few separate threads for the execution of expensive tasks. However, if your app requires resource-consuming computation, it's better to use other languages (for example, Java) on its backend.

  • What is unit testing in Node.js?

    Individual units and components are tested separately in unit testing, which is a software testing method. The smallest testable bit of code in an application is referred to as a unit. Developers are typically running tests during the development phase of an application.

  • Most common Node.js testing frameworks

    There are several frameworks for running unit tests in Node.js, the most prominent of which are Jest, Mocha and Jasmine.

    Mocha has been around since 2011. It functions by using the help of third-party assertions, mocking software and spying software (which keep track of their interaction with other objects or pieces of code). It's extremely expandable, with a plethora of plugins, extensions, and libraries built to operate on top of it.

    Jest is a JavaScript testing framework created by Facebook and updated on a regular basis. It has grown in popularity since 2016, with a whopping 61 percent of JavaScript developers having tried it and intending to use it again.

    Jasmine has been around for a much longer time than Jest, having been developed by Pivotal Labs and launched in 2010. It is designed to operate on any JavaScript-enabled platform, it’s highly flexible and it’s compatible with a number of different testing frameworks and libraries, such as Sinon and Chai. It has a sizable community and plenty of resources—including libraries, blog posts, and tutorials, because of its longevity.

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