20 Full Stack Developer Interview Questions to Ask Programmers

Full-stack developers have a wide range of responsibilities. That’s why business owners can get confused easily wondering what exactly they should assess during a job interview. To help you screen candidates productively, our hiring experts at Bridge helped draw up a list of top junior and senior full-stack developers. By adding these general and technical full stack developer interview questions to a job interview, you’ll have a better grasp of a candidate’s personality. Let’s get to it!

What Should a Full-Stack Developer Know?

Since full-stack developers are actively engaged in every stage of project creation, even junior job candidates should have a strong understanding of all main processes. Here are the crucial skills for an entry-level professional:

Version control (most teams use Git)
Confident command of at least one popular IDE.
Experience in debugging.
Project management methodologies. You want to hire a candidate who has at least a theoretical understanding of Agile, Scrum, Kanban, or other strategies the team uses.

10 General Full Stack Developer Interview Questions

Here are the full stack engineer interview questions that help determine how well a junior developer is familiar with the technologies and concepts of the field.

#1. Which languages and technologies should a full-stack developer know?

This question will give business owners an immediate understanding of how many types of tools a candidate can work with. Typically, the technologies expected in a full stack engineer job description are:

Front-end and back-end programming languages. The former include HTML, CSS, and JS, while the latter are Java, PHP, Python, and others. A candidate doesn’t have to be highly skilled in either – however, a good understanding of syntax and applications will make it easier to collaborate with teammates.
Frameworks. These tools help cut the time needed to bring a product to the market tremendously – that’s why it’s helpful to hire a candidate familiar with the main ones. The examples of most widely used frameworks are Django, Spring, Hibernate, etc.
Databases are the cornerstone of most software development projects. That’s why a full-stack engineer should know how to use at least one DB language – for most candidates, it’s SQL.
Prototyping and design tools. Having a toolset for wireframing, as well as UX and UI design is crucial for designing the front-end of the project.

You can ask developers a few in-depth questions on back-end technologies – here’s a list of PHP interview questions.

#2. What are the strategies you use to optimize a website?

Optimizing a website means increasing its speed and responsivity on low-end devices. There are several strategies full-stack developers use for optimization – a candidate should mention at least one among the following:

Setting up srcset to improve image responsiveness.
Making sure there’s no inline JS and CS.
Gzipping
Leveraging the power of browser caching
Image size compression.

#3. What are your tips for reducing the loading time of a web application?

Usability is a key factor in converting website visitors into leads or active users. That’s why business owners should make sure that candidates take performance seriously and know how to improve the running speed of a WPA.

Here are a few widely used tricks among full-stack developers:

Minimizing the resource load of the page.
Using distributed networks for shared resource files.
Enabling lazy loading to make sure that a part of the page loads only when a visitor is viewing it.

To assess a candidate’s proficiency in web development even deeper, throw a few web developer interview questions into the mix.

#4. What are the most common technology stacks you know?

A full-stack engineer is the one in charge of choosing technologies the project will run on. You want to make sure that your future hire is familiar with the most popular tech stacks used to support high-traffic platforms.

Here is a quick rundown of three widely used technology stacks:

LAMP (short for Linux, Apache, MySQL, PHP) is a go-to stack for most web development projects. Facebook, for one, is built on LAMP.
MERN (short for Mongo.DB, Express, React, Node.js) is a newer tech stack that’s gaining traction among web developers, especially for e-commerce and startup projects.
MEAN (short for MongoDB, Express, Angular.js, Node.js) is a similar stack to MERN, with the only difference being the use of Angular.js instead of React. This set of technologies is a top choice for app development.

#5. What is Continuous Integration? What are its key steps?

Continuous integration is the process of connecting the code written by different full stack developers into a single project. The CI workflow usually goes as follows:

Creating a delivery strategy.
Elaborating a version control strategy.
Developing a development strategy.
Designing a tool that will automate tests.
Configuring a testing environment.
Unit testing.
Functional testing.
Configuring an acceptance environment.
Creating a package for the release to make sure it’s shippable.
Creating an error reporting system.
Backing up automation.

#6. What a three-tier model in an application?

Most applications are built using a so-called three-tier architecture. The main benefit of this approach is breaking down business logic, app design, and data storage into separate modules.

Let’s take a closer look at each layer of the three-tier architecture:

Presentation layer – all the front-end components of the application. This layer determines how the end-user sees the project.
Application layer supports the functionality of an application. Developers use back-end programming languages to design this part of the application.
Data layer consists of the database management system the tech team chose, as well as the information it stores. The database and the back-end layer of the application communicate by exchanging API calls.

#7. What is Bootstrap?

Bootstrap is a highly convenient resource for front-end developers so full-stack engineers should know about it as well. In a nutshell, it is a library of HTML, CSS, and JavaScript components.

Here are the types of components developers can find in Bootstrap:

Grinds.
SaaS variables.
Plugins.
Ready-to-deploy modules.
Plugins.

Full-stack developers use Bootstrap both for prototyping and application development.

#8. What is responsive design? What are its best practices?

Responsive design is an approach to application design that aims to create interfaces that fit various screen dimensions. Given that there are over 20,000 smartphone and computer display sizes, it’s not a challenge-free process.

Here are the practices full-stack developers and designers use to improve responsiveness:

Adding at least three CSS breakpoints.
Prioritizing content by importance ensuring that the most relevant blocks are the most accessible ones.
Making the size of buttons around 44×44 pixels.

#9. Name the differences between architectural and design patterns

While both architecture and design help outline the idea of the application, the former is concerned with the “big-picture-view” while the latter is considerably more detailed.

As for follow-up full-stack software engineer interview questions, you can ask a candidate to describe the main types of architectural patterns and make a few examples of design patterns.

The most widely used architectural patterns are:

Model-view-controller
Layered pattern
Master-slave pattern
Event-driven architecture
Monolithic architecture
Model-view-presenter
REST

The three types of design patterns are:

Creational.
Structural.
Behavioral.

#10. Name a website or application you don’t enjoy using. Why is that the case? What would you change about them?

Asking a series of such full stack interview questions helps business owners find out how creative and analytical the candidates they are interviewing are. For one, you’ll see developers’ approach to dealing with things they don’t like – will they keep griping about someone else’s shortcoming or offer proactive solutions?

Also, you’ll discover the candidate’s personal preference in application design and find out how well they match your personal vision for the project.

10 Technical Full Stack Developer Interview Questions

After getting to know the human side of a job candidate better, business owners should take some time to find out if a developer is ready to walk the walk, not just talk the talk. To discover how skilled a full-stack engineer is in using programming languages and tools, ask the following full stack coding interview questions.

HTML5

#1. What is a data attribute and how to use it?

Data is a custom attribute defined by a developer. It applies whenever there’s no suitable characteristic a developer would rather use. Data is active only for the page where it’s defined and doesn’t require AJAX calls for running.

#2. What is DocType in HTML?

DocType is a command called to the browser that helps to determine the HTML version used to create the page. Developers place DocType before the HTML tag. The data DocType displays come from the document type definition.

#3. Why do developers use Geolocation API in HTML5?

Geolocation API allows engineers to capture a website user’s location. The API tracks the latitude and the longitude of a user’s location and sends this data back to the server. The practical applications of Geolocation API are showing a website visitor her location on the map or letting users know which businesses are located in the area.

#4. What are the main objectives of HTML5?

HTML5 replaced all the previous specifications in order to:

Display rich content types without the need for extra plugins.
Support complex page structures with a wider range of element tags.
Offer cross-platform support.
Simplify error-handling with the help of parsing.

JavaScript

#5. How are Node.js, jQuery, and AJAX different?

Here are the key differences between these three technologies:

Node.js allows running JavaScript code outside a browser.

AJAX allows JavaScript to request data from the server without blocking the system or a need for a user to refresh the page.

jQuery is a JavaScript library designed to automate the execution of AJAX and other tasks.

#6. What do event capturing and event bubbling have in common?

Both Event Bubbling and Event Capturing are ways to propagate events in HTML API. However, the two have conceptual differences. In the case of Event Bubbling, the innermost element is the first one to handle an event after capturing.

On the other hand, when it comes to Event Capturing, the outermost element handles an event after its capture.

#7. Define a callback in JavaScript

A callback function is a function that has been passed to a new function as an argument. Through such callbacks, functions can call each other.

Another advantage of callback functions is that they can run both synchronously (simultaneously) and asynchronously (one after another). In web development projects, they are typically used to perform events before a callback is executed.

Testing a candidate’s knowledge of Node.js is also a good idea – feel free to use our list of Node.js interview questions.

Back-end

#8. Define NoSQL databases and name their types.

NoSQL databases provide tools for storing and retrieving data modeled in non-tabular relations. Here are the main types of NoSQL databases:

Graphs
Column-oriented databases
Key-value databases
Document-oriented databases.

#9. What is the difference between acceptance and functional testing?

Functional testing is a process of verification of whether the processes in the applications are running according to business requirements.

Acceptance testing, on the other hand, is the process of assessing the app against a customer’s needs. This type of testing helps business owners find out whether end-users enjoy interacting with the application.

#10. What are the benefits of the Microservices Architecture?

The microservices architecture approaches an app as a collection of services. Such a model has a lot of objective benefits – here are the fundamental ones candidates should mention at the job interview:

High adaptability to different frameworks and technologies.
Can be used both by SME and large-scale tech teams.
High deployment independence.
The failure of a single microservice does not lead to an application shutdown.

The Bottom Line

A full stack engineer is a key actor in putting two major application components – front-end and back-end together. They need to understand both types of technologies, terminology, and tools used in day-to-day operations of front-end and back-end developers well enough to communicate with both teams.

That’s why taking the time to hire a skilled programmer is so important for shipping scalable, secure products. It’s worth noting that top-notch developers in the US and EU have generally high salaries – that’s why a lot of business owners establish headquarters abroad. To hire an affordable team overseas and manage it comfortably, reach out to Bridge. We provide business owners with around-the-clock assistance and a custom product designed to manage global offices. Find out how our team helps hire top-tier full-stack developers.