Hire senior and proven Fullstack developers

In the last few years, building optimized applications and websites has become more expensive, and at the same time, the demand for quality developers has risen too. On the other hand, developers enrich their skill sets with more than just one programming skill to be more competitive in the market, especially fullstack developers, which are always in high demand.

The question remains: Where to find great fullstack developers, and how to hire them efficiently? First, you start with a winning Fullstack Developer job ad before anything else.

Let's begin.

What is fullstack development?

Fullstack development encompasses the frontend (client-side) and backend (server-side) application development. Fullstack developers work on designing full web apps, websites, and other software from scratch. They also debug, plan, code, and manage the development process. In a way, they take on the role of a team lead that oversees all aspects and stages of development.

Multiple technologies, programming languages, and frameworks are related to fullstack web development and are divided into frontend and backend.

Let's break this down.

Frontend technologies

The frontend refers to the application part that is fully visible to the user. The user operates the elements on the frontend, and this interaction results in poor, good, or excellent UX (user experience) – depending on the its quality, speed, and efficiency. But, a great fullstack developer will cover and optimize all three aspects.

Some of the languages used to create the app frontend are:

• HTML + CSS: HTML stands for HyperText Markup Language, and CSS stands for Cascading Style Sheets. They make the perfect combination for building websites and creating a seamless user experience across many platforms, devices, and browsers. HTML tells the browser what to show, and CSS tells it how.

• JavaScript: JavaScript is a popular scripting language for creating, placing, and monitoring multiple interactive elements on a website. The central JavaScript paradigm combines its many frameworks and libraries (Node.js, Vue.js, Next.js) to create state-of-the-art applications, websites, and other types of software as needed. This language is vastly applicable and a vital part of both the frontend and backend of the app development process.

• TypeScript: If you remove the types, TypeScript quickly becomes JavaScript. Both these share the same architecture because TypeScript is built on top of JavaScript, and if a developer is proficient in one, they will be skilled in the other.

Frontend frameworks

The frontend languages "rely" on the power of frameworks and libraries to improve app functionality and make developers more productive in the long run. Some of the most notable frameworks for frontend development are:

• Angular: Overall, Angular has become more of a platform for building large-scale robust, dynamic, performant applications, improving client-side communication, and ensuring updates run regularly.

• React.js: As a JavaScript framework, React.js is used for building intuitive user interfaces and is one of the most popular frontend frameworks. It is open-source and best known for handling the app's view layer without compromising its quality, speed, and efficiency.

• jQuery: One of the main functions of jQuery is simplifying the data exchange between HTML documents, i.e., the interactions between the DOM (Document Object Model) and JavaScript. This improves the DOM animations and supports cross-browser JavaScript development.

• Vue.js: Vue.js represents a JavaScript framework built on top of JavaScript, CSS, and HTML. Developers use this framework to build simple or complex user interfaces.

Backend technologies

The backend or server side of an app or website handles multiple elements, such as proper API integration, database management, and query management, among other things. Some of the most prominent programming languages, frameworks, and libraries used for backend development are:

• PHP: Considered one of the most popular server-side scripting languages, PHP is widely used for web development backend. Developers like using it to build dynamic content and easily read, write, and delete files on the server, encrypt data, manage control user permissions, and more.

• C++: C++ is a flexible, object-oriented programming language optimizing the website performance while leaving the UX on the frontend intact.

• Python: As a popular programming language, Python is widely used for its simplicity, easy-to-learn syntax, and seamless integration of multiple systems, browsers, and devices.

• Java: A seasoned fullstack developer ideally has an excellent knowledge of Java and writing Java code with this object-oriented scalable language.

• Node.js: There are various definitions of what Node.js is, from a framework to a runtime environment, but it all comes down to being a JavaScript extension for creation, testing, and running backend services.

Backend frameworks

Backend frameworks are a crucial part of fullstack development, and some of the most popular ones are:

• Django: Django is an open-source Python framework for outstanding web design and development. It is fast and uses the MTV architectural pattern (model-template-view).

• Laravel: This is a reliable backend API for Next.js, mobile, and other frontend apps. And, Laravel is a PHP framework that uses the MVC architectural pattern.

• RoR: The abbreviation stands for Ruby on Rails, and this is a robust backend framework based on the language Ruby. It relies on JSON and XML for data transfer and HTML, CSS, and JavaScript to stabilize the UI (user interface).

• Spring: As one of Java's backend frameworks, Spring stands out with a simple syntax and powerful operational logic for the most complex operations. It helps developers create reliable and fast apps through the POJOs (Java objects).

• Express.js: Express.js represents a Node.js web development framework for mobile and web apps. It renders pages dynamically, defines routing tables, and performs various HTTP actions.

When do you need a Fullstack Developer?

There is a notable demand for fullstack developers out there because they wear multiple hats by covering both the frontend and backend aspects of development. With that, they bring excellent problem-solving skills to their work.

But you need a Fullstack Developer if you want a product created efficiently, with minimal fuss, but is highly functional – and the developers make it mostly on their own without significant external support.

A Fullstack Developer is familiar with the whole development process from the start point to the endpoint or from the initial idea to the working prototype. You need a tech expert like this because one person being multi-skilled is an excellent investment for any business. Hiring one fullstack developer instead of multiple tech experts proficient in much less technologies will save you time and money in the long run.

Also, when you hire a quality fullstack developer, they will oversee the whole engagement workflow independently and mitigate the probability of miscommunication in the strict and crucial stages of the app development cycle.

Let's recap:

• They are multifaceted tech experts proficient in frontend and backend
• They deliver reliable and robust code
• They have multiple years of experience in a variety of fields and niches
• They can easily switch roles on the fly (senior, debugger, project lead, and more)
• They are cost-effective tech experts
• They have good knowledge of past, present, and potential future trends in development

Where to find fullstack developers?

You can find fullstack developers in various places, including freelancing platforms, social media, code repositories, word-of-mouth recommendations, and programming websites. However, with these options, you have to do all the research on your own or with your team of in-house recruiters.

Instead, suppose you want to save time and prevent the risk of prolonging and dragging out the hiring. In that case, you can always go for services that match you with ready-to-work developers in just days, such as Proxify, where we also vouch for the background of developers and their technical knowledge, so you don't have to do it all yourself.

Interviewing Fullstack Developers

Here is a checklist of technical skills that a Fullstack Developer needs to know and some interview questions and answers you could use for the assessment.

General fullstack knowledge

An experienced fulllstack developer will know the ins and outs of data structures, algorithms, programming language theory, and network topics such as OSI/RM and TCP/IP protocol models.

Also, they will know how to work with at least three different programming languages and can demonstrate real-world examples of completed engagements in the past.

Last but not least, they need to test and debug efficiently.

Technical skills

In short, they will need to combine some (or majority) of the following skills:

• HTML, CSS
• JavaScript, TypeScript
• React.js, Angular, Vue.js, Next.js, jQuery
• Node.js, Express.js
• Java, Spring
• Python, Django, Flask
• C++, C#
• PHP, Laravel
• Perl
• Ruby, Ruby on Rails

But they should foremost show exceptional knowledge in:

• How HTML and CSS work, separately and together
• HTML code at a cursory level
• Most of the JavaScript frameworks by heart
• Java and most of its frameworks (Spring, Spring Boot)
• Know Python's frameworks excellently (Django, Flask) C++
• Databases (such as MongoDB, PostgreSQL, MySQL)
• Version control systems (such as Git and GitHub)
• Cloud hosting platforms (such as Heroku, AWS, Google Cloud, and Microsoft Azure)

Interview questions and answers for assessment of fullstack developers

We can divide the questions into general and specific.

General questions

1. What programming languages do you have the most experience working with?

Example answer: I have the most experience building applications in Python, Django, and Vue.js, but I also have significant experience with JavaScript, SQL, and Rust. Nonetheless, I like the OS independence that comes with this overall stack, as I can always be sure that my applications will be compatible with the most popular operating systems today.

2. What is your favorite or most frequently used programming language?

Note: Here, the interviewer should keep an open mind regarding the candidate's answers. The developer may suggest a different programming language than the one interviewer had in mind.

Example answer: Ever since I started, I liked working with Python. It has a very intuitive syntax and gentle learning curve (straightforward to learn, hard to master), and it offers a variety of libraries and frameworks if you want to extend the possibilities of what you can do without compromising the quality of the final application.

Choosing just one favored programming language for fullstack development is difficult, so I would also add Node.js and C#. Node.js is great for scalability, boosting performance, and is cost-effective. At the same time, C# speeds up the development process, works on scalability, and is simple to maintain. For a fullstack developer role, all of these benefits go a long way when combined, making our work more accessible and more effective for a superb result.

3. What technologies would enable you to build an application from scratch?

Example answer: Regarding client-side development, I prefer the basics, i.e., HTML, CSS, JavaScript, and maybe TypeScript. To solve database queries, MySQL should get the job done. For the nitty-gritty, I'd prefer to use Python with Django or the LAMP stack for more complex engagements. I also rely on Git and Github for easier synching with other fullstack developers.

4. What are some of the recent fullstack development trends that caught you by surprise?

Example for an answer: I'm fascinated about the rise (and potential downfall) of NFTs (non-fungible tokens). In the past, programming and art were usually considered two separate disciplines. Nowadays, it seems like the boundaries become blurred with each passing day. For example, to create an NFT collection, you must be a decent programmer with a unique artistic touch. The world of NFTs (and cryptocurrency in general) could either take off or crash spectacularly without warning, which I think of every now and then.

Apart from this, there are also worthy mentions such as AI which introduces many new tools that will help (almost) everyone do their job much more efficiently than before.

5. Were there instances where your coworkers made a coding mistake? What did you do?

Note: The interviewer should be prepared to hear the developer's possible answer, as this is a somewhat personal-opinion question.

Example answer: Yes. Once, I was working on a JavaScript engagement with a colleague, and the code wasn't compiling correctly. I went through it manually and found they used parentheses where they should've used brackets, but I stepped up to help fix the error.

6. How do you build SEO-friendly web applications?

Example answer: I use an excellent foundational language (Python) paired with a current type of framework (Django) to solve for efficiency and speed. Building web applications means you don't have the luxury of “hoarding” unused resources that take up unnecessary space, dragging down the entire workflow. SEO is all about fast loading times (users usually click away if the site doesn't load in circa two or three seconds), so I try to use a lightweight approach and solve for SEO before the engagement starts.

7. How do you debug challenging programs?

Example answer: One method that I repeatedly use (and which I think is more effective than developers usually give it credit for) is the so-called “commenting out” method. Once I suspect that an erroneous chunk of code is interfering with the rest of the workflow, I comment out that specific code and recompile the engagement. If the problem persists, I move to browser-based debuggers for web projects (Firefox and Chrome) or desktop-based debuggers for Windows projects (Visual Studio Debugger).

8. What is a common challenge in fullstack development, and the best approach to resolving it?

Example answer: An obvious one is achieving a balance between the frontend and backend and managing them well. It can be challenging to accomplish this because different developers work on other things of the same engagement, so synching between team members is the reason behind this situation.

9. What is the best way to optimize SQL queries?

Example answer: To optimize these queries, we need to recognize the best techniques for improving the performance of the SQL query. Some of the best techniques are:

• SELECT query instead of using SELECT*
• Indexing
• Table aliases
• Not a lot of JOINs used
• Subqueries
• Wildcards
• Database design optimizing

10. Can you define the Callback Hell?

Example answer: The Callback Hell represents an anti-pattern that we can see in the async programming code (basically when many functions run simultaneously). The Callback Hell is also known as the Pyramid of Doom, and basically, these names for it refer to many nested “if” functions or statements. This situation is when many async functions exist simultaneously and depend on one another.

This can create a mess because many callback functions are all in layers and nested. So, when we use callback functions, what is left is a code that is almost impossible to maintain or read and resembles a pyramid shape too. The flow of the app cannot be easily identified as well, and all of this is a debugging obstacle – hence the hellish phrases of this anti-pattern.

Specific questions

1. Are you familiar with design patterns? How have you used them in your engagements?

Example answer: Generally speaking, design patterns are approaches to solving a specific challenge in software engineering. I have used creational and structural design patterns in my previous engagements with great success. I have used the Singleton, Flyweight, and Bridge design patterns.

2. What is the difference between interface and abstract classes?

Example answer: Interface classes only allow you to state the class's functionality but not to implement it. With abstract classes, you can quickly implement functionality using subclasses.

3. How would you define a RESTful API?

Example answer: RESTful API is a type of interface that two computers (usually a client and a server) use to communicate on the web. The RESTful API retrieves a record by a GET request, creates one through a POST request, and deletes one with a DELETE request.

4. What is your proposed solution to prevent a bot from scraping a publicly known API?

Example answer: There are a couple of ways to do this. For example, you can require a username and password from the users (to create an account) to access content on the site. Or, you can limit the number of times a single user can make requests using an identical IP address.

5. What is the difference between normalizing and resetting CSS?

Example answer: Normalizing will only remove a limited number of stylings the browsers pass down to the elements on a page. With resetting, all of the default stylings are removed.

6. What is the difference between blue-green deployment and rolling deployment?

Example answer: A rolling deployment strategy doesn't have multiple staging environments. It deploys updates only on a per-needed basis. Blue-green deployment makes use of two deployment strategies: blue and green. In the blue phase of the BG deployment strategy, the engagement undergoes quality assurance and testing as required. The green phase handles traffic until everything in the blue phase is completed accordingly.

7. How many types of design patterns are there?

Example answer: There are three: structural, behavioral, and creational. Structural patterns increase the functionality of the classes in the code without significant changes to the composition. Behavioral classes depend on the inter-communicability between classes. Creational patterns are meant for class instantiation. They are further divided into object-creational object-creational and class-creational patterns.

8. What are some of the differences between REST and GraphQL?

Example answer: GraphQL is a server-side technology that executes queries to get ahold of data. REST is an architectural style that constrains how web apps are created. Also, GraphQL uses schema, while REST relies on a series of endpoints for its execution.

9. How would you reduce the loading time of a web application?

Example answer: In a couple of ways. First, you can compress the images and move the stylesheet references to the beginning of the HTML page. Next, you can move the script references to the end of the HTML page. Finally, you can separate the JavaScript and CSS code and place them outside the main HTML document.

10. Why would you clear floats in CSS, and how do you do it?

Example answer: We can easily position elements (images mostly) so that content will flow nicely around them through floats. But when we do this, the result may be subsequent elements around the float items, so the layout gets broken poorly. To prevent this, we are clearing the floats, and thus we have much better control over the layout. These are, in my opinion, the two most common and popular clearing floats methods out there:

• Clearfix is the most common one, so we need to apply the technique “clearfix” through a pseudo-element. We must first create an invisible element that clears and floats fast. From this, expect more markup to the HTML too:

group::after {  
content:””;
display:table;
clear:both;
}

11. How would you most efficiently remove ES6 array duplicates?

Example answer: The most common and best way is by using a set – it allows for storing unique values. So, when we convert the array into a set, duplicate values are removed this way. The last step is to do another conversion, this time set to a variety as it was before, with unique values.

12. Can you define and differentiate between async/await and Promises in JavaScript?

Example answer: Async/await represents a 'syntactic sugar' built on Promises on top of it, and it makes an asynchronous code resemble a synchronous one through the usage of async functions and the keyword "await."

13. How would you explain the process of debouncing functions in JavaScript?

Example answer: When we need to postpone the execution of a function, this is called debouncing. We do the postponing to prevent too frequent firing up of time-consuming tasks. One way to debounce a JavaScript function is:

function debounce(fn, delay) {
  let timeoutID; 
  return (...args) => {
    clearTimeout(timeoutID);
    timeoutID = setTimeout(() => fn.apply(this, argos), delay);
  };
}

14. What is the purpose of Event objects for modules such as http or fs in Node.js?

Example answer: The Node.js modules utilize the Event objects to emit events that signal any state changes, errors, or resource availability. Event-driven programming must rely on Event object usage to achieve scalable and efficient apps. This is the case specifically when we work with workloads that are I/O-bound.

15. What could you say about memory leaks? How to spot, resolve, and prevent them?

Example answer: Memory (RAM) leaks represent an app's portion that uses a certain memory but never frees it afterward. When an app uses a lot of memory and doesn’t free it, it will exhaust the memory pool after a while. In the past, memory leaks were common when developers used C++ and C. Detecting this is not too difficult because the most obvious sign is not having enough memory–the system slows down, and the app will start to crash. Preventing this is not too hard either, we just need a good garbage collector to free up memory.

A fullstack developer's point of view

Meanwhile, we inquired about fullstack development straight to the source, two Fullstack Developers of Proxify, Martin Lucka, and Dmitriy Zolotukhin. We asked about essential technologies, the must-know prerequisites, do fullstack developers focus mainly on the backend or frontend, and how they should generally approach learning.

Here is what Martin had to say initially,

"A fullstack developer is a professional (similar to a unicorn) that can develop an app from zero until the final user experience. That includes the ability to build backend (server-less or server-full with databases) and frontend (web or app) products."

And he doesn't hold back regarding the must-know technologies,

"If choosing a serverless solution, then using only frontend technology is sufficient – JavaScript/TypeScript, CSS, React (don't learn Angular, Vue.js, and other frameworks if they’re not required)", he says. "If choosing server-full, knowledge of backend languages (Node.js + TS/JS, Java, C#, PHP) and databases (SQL) are important too."

Regarding the focus and time spent on the frontend or backend, Martin reiterated,

"Usually, the fullstack is just the set of skills, but most engagements have it separated, and then the developer chooses which career path he wants to go. Small engagements might have server-less solutions, where both knowledge subsets would be applied (in that case, it's good to have some cloud knowledge – GCP/Firebase, AWS, Azure, Back4app)."

And for any newcomers arriving to the world of fullstack development, this was the advice he gave,

"Learn React and React Native since I still believe they are the most powerful tools on the market. Don't learn the old way with classes; learn the functional way with hooks. Learn TypeScript as it gives a stable foundation for any engagement. Learn and practice; the best way is to do your own project. If you see that some engagements only use JavaScript and classes and not functional programming and TypeScript, run away as fast as possible."

Dmitriy, shares his thoughts on how to spend time best and focus when developing,

"On real development, try creating your own app and using new technologies, frameworks, and libraries. Read about new technologies and try them out, not just watch from the side or read. Install and use them."

And he adds that it is vitally important to be almost identically proficient in backend and frontend. Still, according to the engagement requirements, developers can adjust their attention to where it is most needed.