Full Stack Developer Interview Questions

Embark on the journey to becoming a versatile full-stack developer with 'Full Stack Developer Interview Questions.' This blog is your comprehensive guide for preparing for full-stack developer interviews, featuring a wide range of questions and detailed answers. Whether you're a seasoned developer or aspiring to become one, our resource covers both front-end and back-end technologies, offering insights into JavaScript, databases, and web development best practices. Equip yourself with the knowledge to excel in full-stack interviews and deliver end-to-end solutions with confidence.

1. What is a Full Stack Developer?

A Full Stack Developer is a professional who has expertise in both front-end and back-end development. They are capable of working with the entire web development stack, from the user interface to server-side scripting and database management.

2. Explain the difference between front-end and back-end development.

Front-end development involves creating the user interface and user experience, typically using HTML, CSS, and JavaScript. Back-end development focuses on server-side logic, databases, and the overall server infrastructure, often using languages like Node.js, Python, or Ruby.

3. Which language is the most preferred by full-stack developers?

Full Stack Developers utilize several programming languages. Ideally, a candidate should be fluent in several languages, preferably some for designing the front end and others for fixing the back end. Since Full Stack developers work with a variety of technologies and applications, they must be proficient in at least two to three of the most popular languages such as Java, Python, Ruby, PHP, C++, etc.

4. What is Callback Hell?

Callback Hell, or Pyramid of Doom, is a common anti-pattern seen in asynchronous programming code (multiple functions running at the same time). This slang term describes a large number of nested "if" statements or functions. In simple terms, Callback hell is a situation where you have multiple asynchronous functions. Those functions depend on one another, so it could get quite messy with so many callback functions nested in so many layers. The use of callback functions leaves you with code that is difficult to read and maintain, and looks like a pyramid as shown below:

This also makes it more difficult to identify the flow of the application, which is the main obstacle to debugging, which is the reason for the famous name of this problem: Callback Hell.

5. What are some of the uses of Docker?

One of the thorniest problems in software development is dealing with the different environments across different machines and platforms. Using Docker, you can isolate your applications from your infrastructure, which is crucial to delivering software quickly. Developers can package and run their applications into containers, executable components that have all the OS (Operating System) libraries and dependencies needed to run the application in any environment. It does not matter what is installed on the host—containers are lightweight and include everything needed to run applications.

  • The code has to pass through many different environments as it travels from the developer's machine to production. Consequently, each of these environments may be slightly different. Using Docker streamlines code development and deployment, as it provides a consistent environment from development to production.
  • Docker's primary purpose is to simplify configuration. With VM (Virtual Machine), you can run any platform with its configuration on top of your infrastructure. Docker offers the same functionality without the overhead of virtual machines.

6. Is there a way to decrease the load time of a web application?

Here are some ways to reduce load times for web applications:

  • Image Optimization: The file size of an image can be dramatically reduced by switching to a different file format. For example, GIFs work well for images with few colors, such as logos, JPEG is ideal for images with lots of colors and details, such as photographs, and PNG format is ideal for transparent images with high quality.
  • Keep JavaScript and CSS in external files: Embedding JavaScript and CSS in HTML documents forces them to be downloaded every time the HTML document is loaded. In this case, browser caching is not utilized, and the HTML document becomes larger. This is why you should always place CSS and JavaScript in external files; it is a best practice and simplifies maintenance.
  • Reducing redirects: Too many redirects will delay the loading time of a website. HTTP requests and responses are delayed each time a page redirects. Getting rid of unnecessary redirects on your site will reduce the load time of your site significantly.
  • Load CSS and JavaScript files asynchronously: Your website contains CSS and JavaScript files that can be loaded either synchronously or asynchronously. As part of synchronous loading, each file is loaded sequentially, in the order it appears on your site. As opposed to synchronous loading, asynchronous loading allows multiple files to be loaded simultaneously, boosting the performance of a website. 
  • Minify HTML, CSS, and JavaScript: If you optimize the way your files load, your pages will load more quickly. You can do the same when it comes to HTML, CSS, and JavaScript code. By eliminating unnecessary spaces, characters, and comments, you can reduce the size of your files. This will make your web pages load faster.

7. Explain inversion of control.

IoC (Inversion of Control), as the name suggests, is a design principle in software engineering. With IoC, different kinds of controls can be inverted in an object-oriented design to attain loose coupling. The term "controls" refers to any other responsibilities a class may have other than its primary responsibility. These include controlling the flow of an application, controlling the creation of objects, or controlling the binding and creation of dependent objects. IoC allows classes to be loosely coupled, making testing and maintenance easier. 

8. What do you mean by referential transparency in functional programming?

In functional programming, referential transparency is the key differentiating factor.  An expression is considered referential transparent if it can be replaced or substituted with the corresponding value it computes or vice-versa without affecting the program’s result.

Example: Imagine that we have an expression called four: val four= add(1,3)

If four is used anywhere in our code, it can safely be replaced with add(1,3), 1 + 3 or 4 wherever it appears. Thus, all the expressions below are equivalent in meaning and output:

val eight = four + fourval eight_v2 = add(1,3) + add(1,3)val eight_v3 = 4 + add(1,3)val eight_v4 = 8

If we can swap back-and-forth between these expressions anytime, anywhere, without altering their meaning or output, then an expression is referentially transparent.

9. In Java, what is a connection leak? How can you fix this?

If a connection is opened and forgotten about, this is known as a "leak" since each time it occurs, a connection is no longer available for reuse. Connection leaks occur when some database requests or transactions are not closed properly or are not committed, causing the connections to be abandoned and closed permanently.

Java developers commonly experience Connection Leaks when using Connection Pools. In the case where there is a section of code that fails to close a connection properly, a connection will leak from the pool each time the section of code is executed. Eventually, if this situation continues, the pool will run out of connections, which is known as Pool Exhaustion. The application will hang once all available connections have been leaked. We can fix this by closing the connection and paying particular attention to any error handling code.

10. What is Promise and explain its states?

Callback functions are functions that can be passed to another function as arguments and executed there to complete a routine or action. Those functions depend on one another, so it could get quite messy with so many callback functions nested in so many layers. This is what is referred to as callback hell.

As an alternative to callbacks in JavaScript, promises are used to handle asynchronous operations. In addition to handling multiple asynchronous operations, they provide better error handling than callbacks. Promises can be a better way for a user to read the code effectively and efficiently, especially when that particular code performs multiple asynchronous operations. The Promise object represents the result of an asynchronous operation (or its failure) and the resulting value. The promise is in one of the following states:

  • Pending: In its initial state, neither fulfilled nor rejected.
  • Fulfilled: Indicating that the operation was successful.
  • Rejected: Indicating that the operation failed.

11. State the difference between GET and POST.

GET and POST are two different HTTP request methods.

This method is used to request data from a certain resource (via some API URL). This method is used to send or write data to be processed to a specific resource (via some API URL).
If you use the GET method to send data, the data is added to the URL, and a URL can be up to 2048 characters in length. Therefore, it has restrictions on data length. It does not impose such limitations.
In comparison to POST, GET is less secure since data is sent as part of the URL. Passwords and other sensitive information should never be sent using GET. It is a little safer to use POST than GET because the parameters are not saved in the browser history or the web server logs.
Everyone can see the data in the URL. There is no data displayed in the URL.

12. Explain the Restful API and write its usage.

APIs (Application Programming Interfaces) are sets of rules and protocols that define how software programs or devices can communicate with each other. APIs that conform to the design principles of REST, or representational state transfer, are known as REST APIs. REST APIs may also be referred to as RESTful APIs. Using RESTful APIs, developers can create requests and receive responses via an HTTP request. REST API can also be used for mapping data from a cloud platform to a data warehouse or vice versa.

13. What do you mean by MEAN Stack?

MEAN stands for MongoDB, ExpressJS, AngularJS, and Node.js. It is a collection of JavaScript-based technologies for developing web applications. Despite being a stack of different technologies, all of them are based on the JavaScript language. It is an ideal solution for building dynamic websites and applications as it is a very user-friendly stack. With this free and open-source stack, you can quickly and easily build web-based prototypes.

14. Do you know how to prevent a bot from scraping your publicly accessible API?

As long as the data within the API is accessible to the public, it will technically not be possible to completely prevent data scraping. It is possible, however, to minimize bot activity (automated computer programs on the internet that perform certain tasks) by throttling or rare limiting. Rare limiting will be able to prevent a certain device from making an unlimited number of requests within a defined time. If too many requests are made beyond the defined limit, a 429 Too Many Attempts HTTP error is thrown. It is vital to record more than just the IP address of the device since the IP address is not unique to each device and can stop the whole network from accessing the API.

15. What makes MVC (Model View Controller) different from MVP (Model View Presenter)?

Developers prefer to develop Android applications by utilizing a software architecture pattern. Architecture patterns allow you to express and define a structural schema for software systems. Developers can easily maintain the software and continue to add features to the software in the future. The two most popular android architecture patterns are MVC (Model View Controller) and MVP (Model View Presenter).

MVC suggests splitting the code into three components. As soon as the developer creates a class or file for an application, he or she must categorize it into one of three layers: Model, View, and Controller. This is an architectural pattern that helps compensate for some of the shortcomings of MVC. It is composed of three components i.e., Model, View, and Presenter.
The controller serves as a bridge between the view and model layers and therefore provides the application's user interface. As soon as the Model changes, the Controller updates the View. The presenter pulls data from the model and applies the UI  (user interface) logic to determine what to show. In response to the user's input notification, it manages the state of the View and takes appropriate actions.
Controllers and views have a many-to-one relationship since one Controller can select different Views depending on the operation required. Presenter and View have a one-to-one relationship since the Presenter class manages only one View at a time.
Support for unit testing is limited.  The unit testing process is highly supported.

16. What do you mean by Temporal Dead Zone in ES6?

Before ES6, variable declarations were only possible using var. With ES6, we got let and const. Both let and const declarations are block-scoped, i.e., they can only be accessed within the " { } " surrounding them. On the other hand, var doesn't have such a restriction. Unlike var, which can be accessed before its declaration, you cannot access the let or const variables until they are initialized with some value. Temporal Dead Zone is the time from the beginning of the execution of a block in which let or const variables are declared until these variables are initialized. If anyone tries to access those variables during that zone, Javascript will always throw a reference error as given below.

console.log(varNumber); // undefinedconsole.log(letNumber); // Throws the reference error letNumber is not definedvar varNumber = 3;let letNumber = 4;

Both let and const variables are in the TDZ from the moment their enclosing scope starts to the moment they are declared.

17. Why should arrow functions not be used in ES6?

One of the most popular features of ES6 is the "arrow functions" (also known as "fat arrow functions"). Arrow functions are a new way to write concise functions. Arrow functions offer a compact alternative to traditional function expressions, but they have limitations and cannot be used in every case.

The following is an ES5 function:

function timesTwo(params) {        return params * 2     }timesTwo(5);  // 10

The same function can also be expressed as an arrow function in ES6 as follows:

var timesTwo = params => params * 2timesTwo(5);  // 10

Differences & Limitations:

  • Has no bindings to 'this' or 'super', so it shouldn't be used as a method.
  • Has no keyword.
  • The call, apply, and bind methods are not suitable since they rely on establishing scope.
  • Not suitable for use as constructors.
  • Not possible for an arrow function to use the yield keyword within its body, etc.

18. Tell me about a project that you worked on and the technologies you used. Why did you choose them?

With this question, the interviewer can figure out the methodology of the full stack web developer and determine if he is sharp and precise in selecting the right toolset.

While explaining the reasons for choosing a particular toolset, you should be as specific as possible. You must demonstrate that you can develop both the front and backend of the web application. Having more experience on one side of the development game than the other is okay, but you should show you are capable of handling both ends of the application.

19. How many types of full-stack developers are there?

Following are the most common types of full-stack developers based on their specific stacks:

  • MEAN Stack (MongoDB-ExpressJS-AngularJS-NodeJS).
  • MERN Stack (MongoDB-ExpressJS-ReactJS-NodeJS).
  • LAMP Stack (Linux, Apache, MySQL, PHP).
  • LEMP Stack (Linux, Nginx, MySQL, PHP).
  • Full-Stack Python.
  • Full-Stack Elixir.
  • Full-Stack Django.
  • Full-Stack Java.
  • Full-Stack Ruby on Rails.

20. Which full stack is best?

One of the most popular tech stacks is the MEAN stack (MongoDB-ExpressJS-AngularJS-NodeJS). MEAN stack has many applications, including cloud application development. MongoDB, Express.js, AngularJS, and Node.js are among the JavaScript technologies in MEAN used to build web applications.

21. Code Snippet: Simple Express.js Server

const express = require('express');
const app = express();
const port = 3000;

app.get('/', (req, res) => {
    res.send('Hello, World!');

app.listen(port, () => {
    console.log(`Server is listening at http://localhost:${port}`);

22. Online Resources:

Published On: 2024-01-17