How to Hire Full Stack Developers: What You Need to Know

Before you hire Full Stack developers, you must understand their full profile.

A Full Stack Developer – is a specialist who created both sides of an application: frontend and backend.

Front End (client) side – is everything a site or application user sees and interacts with.

Back End (server) side – is responsible for the logic and processing of user interaction in the application: user requests, work with the database, API for transferring data. In a nutshell, this is the “brain” of the application.

The Bureau of Labor Statistics forecasts an 8% growth of vacancies for web developers and a 22% growth for software developers in the period from 2019 to 2029. Currently, the ability to create and maintain a system from beginning to end, i.e. from interface to backend, is highly valued. Therefore, we can say with confidence that full-stack developers are in high demand in the labor market.

Some of the responsibilities of a Full Stack Developer

Core responsibilities of a full stack developer include:

• Creation of front end and back end architecture;
• Implementation and management of projects applying certain programming languages;
• Testing and debugging, bug fixes;
• Work with databases, cloud storage, network resources, etc.;
• API design and development;
• Monitoring of web applications and infrastructure performance.

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Essential skills for a Full Stack Developer

A combination of certain skills is required to enable the proper fulfillment of full stack developer duties. They can be divided into two corresponding parts: front end and back end skills.

Front-end skills are quite similar for all full-stack developers. We list the following of them here:

1. JavaScript (+ HTML and CSS);
2. such libraries as jQuery, React.js, Backbone.js;
3. SASS metalanguage and LESS stylesheet language;
4. such frameworks as Angular.js/Angular, Vue.js, Bootstrap;
5. DOM, AJAX, JSON technologies.

Backend skills make it a bit more complicated. They can be categorized depending on a programming language or a platform that a developer uses:

To be considered a full stack developer a specialist should have a general scope of front-end skills and be able to work with the backend. The backend language is not that important, and it is a platform that matters. For instance, it is important to distinguish the Java platform from the Java language. The Java platform can use different programming languages: Java, Scala, Kotlin, but they all are executed in JVM (Java Virtual Machine).

Skills required from Node.js-full stack developers:

• JavaScript language;
• Node.js;
• Frameworks suitable for Node.js: Express.js, Nest.js;
• Package managers for JavaScript;
• Web Sockets and REST API.

Skills required from Python-full stack developers:

• Python programming language;
• Django/Flask framework;
• REST API;
• OS Linux and Nginx web server;
• Cloud services.

Skills required from Java-full stack developers:

• JavaScript language;
• API Java EE specification;
• Spring (Spring MVC, Spring Boot, Spring REST, Spring Web) framework;
• HTTP-server Apache;
• Google Cloud, and Azure cloud services;
• Servlets, JSP, and microservices.

Skills required from PHP-full stack developers:

• PHP language;
• Framework Yii2/Symfony/Laravel.

In addition to the above-mentioned technologies all full-stack developers should also:

• Know Git version control system + GitHub IT-projects hosting service;
• Be able to work with database functions such as storage, creation, control, processing, and deletion of data: in SQL (usually PostgreSQL or MySQL); in NoSQL (MongoDB for example);
• Be familiar with HTTP and HTTPS protocols;
• Know containerization platforms (Docker) that enable the transfer of software with all the necessary dependencies to clients without the need to re-configure them.

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Full Stack Developer interview questions

In terms of seniority, developers are divided into Junior, Middle, and Senior levels. The developer’s level speaks about his skills and salary. Learn more about every level and which is needed for your particular purposes in our article 5 Software Developer Levels: Whom to Choose.

The level of the developer will also determine what you should check in the interview.

Traditionally an interview is split into two parts. The first one includes theoretical questions. The second – practical task (coding task).

This module covers only the first stage of the interview: technical questions.

We split questions into the front-end and back-end parts to simplify understanding.

Here we list a couple of questions as an example. A more exhaustive list of questions for a full-stack developer can be found in Github.

Frontend part related questions

Q1. What’s the difference between an id and a class? (CSS question)
A1.

• id – is a selector in CSS that is used to apply a style to unique elements of the web page. Uniqueness means single use of an element on the page: header, navigation menu, footer, etc.
• class – is a selector in CSS that styles the selected elements with the specified class. Unlike id, the class allows applying your own style to several elements on the web page, not a single one.

Q2. Can an HTML element have multiple classes? (HTML question)
A2. Yes. HTML-element can have several classes. To do so, the syntax “class=”class-one class-two class-three …” is used.

Q3. What is the difference between a load and DOMContentLoaded events? (JS question)
A3.

• The DOMContentLoaded event is called when the source HTML document has been fully loaded and processed without waiting until style tables, images, and scripts are loaded.
• The load event is run only after DOM and all the dependent resources are loaded.

Find more front-end questions here and here.

Backend part related questions

Node.js full-stack developer:

Q1. Junior. Is it possible to run a Node process without V8?
A1. You need a JS-engine to run the Node process. However, V8 is not the only available engine to do this. Chakra can be used alternatively.

Q2. Middle. How can we avoid callbacks?
A2. To avoid callbacks, one of the following options can be considered:

• Promises. Provide a result that will be available in the future;
• Async/await. This is a new technique to write promises when asynchronous code looks synchronous;
• Yield with Generators and Promises.

Q3. Senior. What is the difference between process.nextTick() and setImmediate()
A3.

• process.nextTick() – allows executing callback-functions passed to it right after finalization of the current function. Callback-functions passed within the process.nextTick() usually are called at the end of the current execution cycle.
• setImmediate() – callback-functions will be called in the next cycle following processing of input/output events.

Python full-stack developer:

Q1. Junior. What does «self» mean in Python?
A1. «self» – is a keyword used to determine an example of a class object. In Python, it is used as the first parameter. Self helps to distinguish methods and attributes of class from its local variables.

Q2. Middle. What is the difference between remove, del, and pop?
A2.

• remove() removes the first matching value.
• del removes an element by its index.
• pop() removes an element by its index and returns this element.

Q3. Senior. Give an example of file processing mode by Python?
A3. There are the following modes:

• Reading mode (‘r’): open file for reading. Default mode.
• Writing mode (‘w’): open file for writing. If the file already exists, the contents of the previous file are deleted. A new file is created.
• Reading-writing mode (‘rw’): open file for reading, writing modes. Renewal mode.
• Appending mode (‘a’): opens the file to writing. If a file exists, the information is added at the end of the file.

Java full-stack developer:

Q1. Junior. How does Java provide high performance?
A1. To provide high-performance, Java uses the Just In Time compiler. It is used to transform instructions to byte-codes.

Q2. Middle. Override vs overload, what is the difference?
A2.

• override – ability to predetermine method behavior in inheritance types.
• overload -ability to redefine a method with a single name, but with a different set of arguments.

Q3. Senior. Can Enum extend a class?
A3. No, it can not, as enumeration is a subclass of the default universal Enum class where T presents a universal type of enumeration. It’s nothing but a general basic class for the enumeration types in the Java language.

Transforming enum to a class is made by a Java compiler within a compilation process. This extension is not clearly stated in the code, but it is always invisibly present.

PHP full-stack developer:

Q1. Junior. What are the three visibility fields for variables in PHP?
A1. Public. The class inside of which the variables are located as well as its examples (objects) can read and change them.

• Protected. Accessible only to a class inside of which they are located and all the inherited subclasses.
• Private. Accessible only to a class inside of which they are located, however, inherited subclasses don’t have access to them.

Q2. Middle. What is the difference between while and do while cycles?
A2. The do-while cycle checks the condition following the execution of all the operators in the body of the cycle. The while checks the condition in the beginning. If the condition is met, the operator is executed inside the cycle.

Q3. Senior. There is an array[1,2,3,4,5,6,7]. What should be done to reverse it and get [7,6,5,4,3,2,1]?
A3. To reverse the array, the array reverse() function can be used.

Additional questions for back-end developers can be found here.

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Cost to hire Full-stack developers

Location and the stack of the developer will eventually affect your budget and costs.

Leading countries currently in demand for full-stack developers and their annual salaries are listed below (data from PayScale, Glassdoor, and Neuvoo):

If it is challenging to find full-stack developers in your city/country, or their rates are too expensive, you might consider hiring a developer using a dedicated collaboration model. This will help you save money and still hire a qualified specialist.

You will find out where to look for developers in our article How and Where to Find Software Developers Who Meet your Needs.

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Conclusion

Hiring a Full stack developer in 2021 is not an easy task, as qualified talents are in high demand. However, the process of picking the candidates is not that frightening when you have an understanding of what attention should be paid to.

We hope that the information above helped you better understand how to hire full-stack developers for your project.