Full Stack Developer Interview Questions

A full-stack developer is an expert in every aspect of software development. Full-stack developers are those who can create both the user interface and the underlying infrastructure. These developers are highly sought after because of their adaptability and their familiarity with many phases of the software creation process.

The demand for skilled full-stack developers reflects this trend. In the United States alone, there are around 30,000 job openings for full-stack developers right now. Indeed reports that the average compensation for this field is just over $100,000, putting it among the highest-paying jobs out there. Join our full stack training in Chennai to upskill yourself.

While full-stack developers can expect lucrative wages and promising futures, finding work in the field can be challenging. Explore our full stack developer interview questions and answers to land your job.

Because of the critical nature of the work, organizations are willing to pay more to attract and retain qualified individuals in this field.

We’ll be discussing the most common full-stack developer interview questions and how to answer them here.

1. What tools and languages, or set of abilities, does a full stack developer require to create a product from scratch?

The following is a list of skills that a full-stack developer needs to have:

• Programming Languages: Full-stack developers should have a strong command of more than one programming language, including but not limited to Java, PHP, Python, Ruby, and C++, among others.
• Technologies used on the front end: You should be conversant with front-end technologies such as HTML5, CSS3, JavaScript, and other similar languages. It is also vital to have knowledge of third-party libraries such as Ajax, jQuery, Angular, ReactJS, and other similar programs.
• Frameworks: This necessitates competence across various development frameworks, such as  PHP, Django, Spring, Spring Boot, Hibernate, and MyBatis, amongst others.
• Databases and caching: In order to be considered a full stack developer, you need to have a solid understanding of several DBMS (Database Management System) technologies, such as MySQL, SQLite, Oracle, and MongoDB. A fundamental familiarity with caching methods such as Redis, Memcached, and Varnish can prove to be quite useful.
• Ability in Designing: If you want to be a great Full-Stack web developer, it is also vital to have a solid understanding of design. In addition to this, the individual should be familiar with the fundamentals of prototyping as well as UX/UI design.
• Server: Previous experience with either Apache or NGINX is highly desirable. When it comes to running servers, having a solid understanding of Linux is quite helpful.

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2.. Which programming language do the majority of full-stack developers favor the most?

Full-Stack Developers are proficient in a number of different programming languages. A candidate should ideally be fluent in many languages, with the goal being to use certain languages for developing the front end and other languages for addressing the back end. Because

Full Stack engineers work with a wide range of software platforms and applications, they are required to have a strong command of at least two to three of today’s most widely used programming languages, including Java, Python, PHP, C++, Ruby, and others.

3. Define the term “pair programming.”

In pair programming, two programmers collaborate and work together while sharing a single computer. During the process of development, one programmer will take on the role of the driver who codes, while another will play the role of the observer (navigator), whose responsibilities will include ensuring that the code is written correctly, proofreading and spell-checking it, and determining where to proceed next.

Any time is a good time to switch roles; for example, the driver can become the observer, or vice versa. Alternate names for this technique include “pairing,” “paired programming,” and “programming in pairs.”

Advantages:

• Should the driver experience any difficulties with the code, utilizing both of them will rectify the situation.
• When working on the same software, the two programmers are just 15% slower than they would be if they worked independently, instead of being 50% slower.
• It is likely that the quality of your code will improve if another programmer reviews it after it has been completed by you. According to the findings of one study, the resulting code contains 15% fewer errors than that which was generated by a single programmer.
• It results in increased collaboration, greater overall quality, improved code, and continuous improvements to development practices.
• As a result of everyone learning from one another over the course of the project, the flow of information is streamlined and accelerated.
• The team improves their ability to communicate with one another.

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4. List some of Docker’s most common applications.

Dealing with the various environments that exist on various machines and platforms is one of the most difficult challenges that arise in the process of developing software. Docker allows you to separate your applications from your infrastructure, which is an essential step in the process of delivering software in a timely manner.

The application can be packaged and executed by developers in containers, which are components that are executable and contain all of the OS libraries and dependencies that are required to run the application in any environment. It makes no difference what software is installed on the host system because containers are small and already contain all of the components necessary to run applications.

During its journey from the machine used by the developer to the machine used in production, the code is subjected to a wide variety of circumstances. As a direct result of this, each of these settings might have some unique characteristics. Docker is a containerization tool that speeds up the process of developing and deploying code by providing a consistent environment at all stages of the process, from development to production.

The major objective of Docker is to reduce the complexity of configuration. You are able to execute any platform together with its settings on top of your infrastructure by using VM, which stands for the virtual machine. Docker provides the same capabilities as virtual machines but without the overhead of running them.

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5. CORS (Cross-Origin Resource Sharing) – what does that mean?

Cross-origin resource sharing is what is meant by the acronym CORS. It is a technology built into browsers that enable web pages in one domain to have controlled access to resources located in other domains (also known as cross-domain requests).

This enables scripts that are executed on a browser client to interact with resources that originate from other origins and gain access to those resources. The Same-Origin Policy (SOP) is therefore extended, and greater flexibility is provided as a result of this action.

The ability of a website to access resources hosted on domains other than its source domain can be hindered by same-origin rules. Because of the SOP, a JavaScript application, for instance, that intends to place a call to an API (Application Programming Interface) that is hosted on a different domain will be prevented from doing so.

In order to get beyond the limitations imposed by policies with the same origin, a CORS policy was put into effect.

In addition, if the CORS policy of a website is not properly configured, then the website may be susceptible to attacks that are launched from other domains. Because of this, it is unable to defend against attacks of the cross-origin variety, such as CSRF (Cross-Site Request Forgery).

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6. Describe what is meant by the inversion of control.

As its acronym, IoC (Inversion of Control), suggests, this concept is a design idea utilized in software engineering. To achieve loose coupling in an object-oriented architecture, many kinds of controls can be inverted with the help of inversion of control (IoC).

The word “controls” is used to refer to any additional obligations that a class may have in addition to its core responsibility. regulating the flow of an application, regulating the generation of objects, or controlling the binding and creation of dependent objects are all examples of these types of controls. Classes are able to be loosely connected thanks to IoC, which makes testing and maintenance much simpler.

7. What exactly is this “Callback Hell”?

The anti-pattern known as Callback Hell, sometimes known as the Pyramid of Doom, is frequently found in asynchronous computer code (code that has numerous functions operating at the same time). A lot of “if” statements or functions that are nested within one another are referred to by this slang word.

In its most basic form, the phrase “callback hell” refers to a circumstance in which numerous asynchronous functions coexist. Because these routines are dependent on one another, the situation has the potential to get rather muddled because there are so many nested callback functions in so many layers.

The use of callback functions will result in code that is not only difficult to read but also difficult to maintain. This code will have the appearance of a pyramid, as seen in the following example:

This makes it more difficult to determine the flow of the application, which is the primary impediment to debugging. Because of this, the problem is commonly referred to as “Callback Hell,” which is a renowned name for this issue.

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8. Describe dependency injection in detail.

A design pattern known as the Dependency Injection (DI) pattern is used to accomplish the Inversion of Control (IoC). It is possible to build dependent objects outside of classes and then make them accessible to classes using a variety of methods. The following are the three categories of classes that are involved in Dependency Injection:

• Client Class: A client class, often known as a dependant class, is a type of class that is dependent on the service class.
• Service Class: Service classes, also known as dependency classes, are the classes that client classes depend on to receive services.
• Injector Class: This class is responsible for transferring items between the service class and the client class.

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9. Explain Long Polling.

Long polling is a technique that is used in the construction of online applications, and its purpose is to transfer information and data from servers to clients as soon as possible. Long-polling ensures that a connection is kept open between the client and the server whenever the client sends a request to the server. This connection will remain open until the data is prepared to be transmitted from the server to the client.

The connection between a client and a server is not immediately severed when the server receives a request from a client; rather, the connection is severed until after the server has returned the data to the client or when a predetermined timeout threshold has been achieved (connection timeout).

10. What is meant by “Continuous Integration” (CI)?

As its name suggests, Continuous Integration (CI) refers to the practice of automating and integrating new or updated code into a single software project on a frequent basis (usually many times per day). This DevOps practice enables developers to incorporate their modified code into a centralized repository so that automated tests and builds can be executed. This is the objective of the practice.

Before integrating the new code into the system, automated tools are used to verify that it is valid. The most important component of the CI process is a source code version control system. In addition, the version control system is complemented by other inspections, such as automated code quality tests, tools for reviewing syntax and style, and a great deal more.

The primary advantage of integrating at regular intervals is that it enables errors to be discovered more rapidly and with less effort. Because the majority of modifications that are introduced are quite minor, it is simple to identify the specific change that resulted in a fault.

The term “Mean Time to Resolution” (sometimes abbreviated as “MTTR”) refers to the amount of time it takes to fix a problem after it has been reported.

When Continuous Integration (CI) is implemented into an organization’s development process, the likelihood of having noncritical problems on a backlog decreases. Before the product goes into manufacturing, these minor flaws are inspected and repaired so that it can be sold to the general public.

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11. In JavaScript, what do “event bubbling” and “event capturing” mean?

JavaScript’s ‘Event Flow’ refers to the process through which events spread over the DOM (Document Object Model). An event’s sequence of arrival to a given web page is defined by its “event flow.” As a result, the following factors affect how JS events propagate:

With Event Bubbling, the event is caught and processed by the innermost element before it bubbles up to the rest of the system. All the way to the root of the DOM tree, events go up the hierarchy from their child elements.

Event Capturing involves the outermost element catching and processing the event before passing it along to the innermost element. Wrapper elements are the starting point for event propagation, and target elements are the last stop.

12. Describe the significance of multithreading.

A process (or an application) that is being carried out is said to be “threaded” when a thread is referred to as a distinct component or part of the process. The concept that we refer to as “multithreading” describes the simultaneous execution of numerous threads within a single process. One way to conceive of it is as a means via which an application can perform multiple tasks at once.

• The employment of several threads in a single process allows for more efficient utilization of available computer resources, which is one of the many benefits.
• Requests made by one thread do not prevent requests made by other threads from being processed, which results in an improvement to the application’s response time.
• As a consequence of this, even if one of the threads has an exception, it won’t have an effect on the other threads.
• On the other hand, compared to simultaneously operating numerous processes, multithreading requires a smaller amount of system resources.
• When compared to the overhead, time use, and administration involved with establishing threads, the overhead, time usage, and management associated with creating processes are significantly higher.

13. Give an explanation of both the advantages and the disadvantages of employing the “use strict” command.

A new feature in ECMAScript5 known as strict mode enables you to execute a program or function within a strict operating context. This feature was introduced in ECMAScript5. Due to the stringent nature of the context, certain actions are consequently unable to be executed, and further exceptions are thrown.

When the statement “use strict” is executed, the browser is given the instruction to utilize the “strict” mode, which provides a JavaScript feature set that is more restricted and therefore safer. If you want to evaluate the JS in strict mode, you can do so by specifying “use strict” at the very beginning of a function.

Your program will be more robust, clear, and accurate if you compile it using the strict option, which causes more errors to be thrown and disables several functionalities.

Advantages:

• When certain common coding flaws are identified, the system will throw errors.
• Errors that make it difficult to optimize JavaScript engines can be remedied if the language supports the strict mode. There are occasions when code written in strict mode runs quicker than code written in a non-strict mode that is otherwise identical.
• In most cases, it stops an “unsafe” action from occurring or generates an error message when one is attempted (for instance, accessing the global object).
• It disables features that were poorly thought out or confusing.
• The process of writing “secure” JavaScript is made easier by using the strict mode.

Disadvantages:

• There is a significant lack of functionality that is utilized by the majority of developers.
• There is no longer any way to gain access to the function. caller or the function.arguments properties.
• It’s possible that you’ll run into issues if you concatenate scripts that were produced using separate strict modes.

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14. What can be done to speed up a web application’s load time?

The load times of online applications can be improved in a number of ways, including the following:

• Image Optimisation

Changing an image’s file format can significantly reduce the amount of space it takes up on our computer’s hard drive. For instance, GIFs work well for images with limited colours, such as logos. JPEGs, on the other hand, are perfect for images with lots of colours and details, like photographs. The PNG format, on the other hand, is perfect for images that are transparent and of high quality.

• JavaScript and CSS should be stored in separate files

When JavaScript and CSS are embedded in HTML documents, it is necessary for each instance of loading the HTML content for them to be downloaded. In this scenario, the browser’s caching feature is not put to use, which results in the HTML document growing in size. It is for this reason that you should always place CSS and JavaScript in external files; doing so is a recommended practice that makes maintenance easier.

• Reducing the number of redirects

A website’s loading time will be slowed down if it contains an excessive number of redirects. The timing of HTTP requests and answers is thrown off whenever a page is redirected. Eliminating all of the pointless redirects on your website will make a substantial improvement to the loading speed of your website.

• Asynchronously loading the CSS and JavaScript files

The website contains CSS and JavaScript files, which can be imported either synchronously or asynchronously depending on your preferences. Each file is loaded one at a time as part of the synchronous loading process, and it does so in the order that it appears on your website.

A website’s performance can be significantly improved by using asynchronous loading, which, in contrast to synchronous loading, enables many files to be loaded at the same time.

• If you optimize the way your files load, your web pages will load more rapidly.

To do this, you should minimize your use of JavaScript, CSS, and HTML. You are able to accomplish the same thing with code written in HTML, CSS, and JavaScript. You can reduce the size of your files by getting rid of any extra spaces, characters, or remarks that aren’t needed. Your web pages will load much more quickly as a result of this change.

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15. Explain in detail the “observer pattern”

The observer pattern is utilized whenever a number of items are connected to one another through one-to-many relationships. When one item is changed, all of its dependent objects are automatically notified and updated. This happens every time the object is changed. This is something that can be classified as a behaviour pattern.

It not only supports broadcast-style communication but also offers a description of the coupling that exists between the objects and the observer. When one object observes the state of another object, that first object is referred to as the observer, and the object that is the focus of the observation is referred to as the subject.

16. Distinguish blue/green deployment and rolling deployment.

The software that is used today is developed quickly, and its features are frequently modified in response to the requirements expressed by customers. After this, the program is put into production. Every company has its own one-of-a-kind process for introducing newly developed apps into production environments.

Standard deployment and release strategies, such as blue-green and rolling deployment, are followed by the vast majority of organizations today.

Blue-green deployment

A deployment approach such as this one, known as the blue-green deployment strategy, produces two distinct infrastructure environments, known respectively as blue and green. A green environment (production) contains the most up-to-date code (new version), while a blue environment (testing) contains older code (an older version). At any given time, there is only ever going to be one production environment that is live.

For illustration, the green environment is active and is processing all of the user traffic, whilst the blue clone is not doing anything at the moment. When a new version of an application is finished being developed and is ready to be distributed, the program can be deployed to the blue environment for testing purposes.

The colour of the application traffic changes from green to blue as soon as the testing phase of the new release is complete. After that, Green will go idle and get ready for testing the next release, while Blue will take over the live production environment.

Rolling Deployment Strategy

By utilizing this method of application deployment, older iterations of a program are wholly supplanted by their more up-to-date counterparts, while at the same time, the underlying infrastructure on which they function is entirely overhauled.

For illustration purposes, when it is necessary to deliver a new version to all nodes, the new version is initially only deployed to the first node, while the remaining nodes take care of end-user traffic. It will begin managing end-user traffic as soon as the new version is successfully installed on the first node, and it will continue to do so even as the new version is being deployed on the second node.

This step is performed as many times as necessary until all of the nodes have successfully been upgraded to the newest version.

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17. How do you define a connection leak in Java? What can you do to make it better?

A “leak” happens when an opened connection is left open without being used, preventing that connection from being reused by other processes. When database requests or transactions aren’t properly closed or committed, they leave open connections that are eventually closed for good, resulting in a connection leak.

When working with Connection Pools, Java programmers frequently encounter Connection Leaks. When a piece of code is executed that should properly end a connection but doesn’t, a connection is lost from the pool. If this situation persists, the connections in the pool will be exhausted, leading to Pool Exhaustion.

Once all of the application’s connections have been disclosed, it will stop responding. By breaking the link and inspecting the error handling code closely, we can get this fixed.

18. Describe the different Promise states.

An example of a callback function is a function that can be used as an argument in another function. Having so many nested callback routines that depend on one another might quickly get complicated. Callback hell describes this situation perfectly.

In JavaScript, promises are used instead of callbacks to manage asynchronous tasks. They offer superior error handling than callbacks and can manage numerous asynchronous activities at once. For a user to be able to comprehend the code successfully and efficiently, he or she must be able to recognize the difference between the two. The Promise object stores the value and status of an asynchronous operation, whether successful or not. The guarantee can take one of several forms:

• Pending: Initially, neither accepted nor rejected.
• Fulfilled: A sign that the procedure was successful.
• Rejected: Signifying that the operation was unsuccessful/failed

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19. Describe and demonstrate how to use a Restful API.

To put it simply, APIs (Application Programming Interfaces) are a collection of standards and protocols that govern the interaction between various pieces of software or hardware. REST APIs are application programming interfaces that follow the REST (representational state transfer) architectural style. It’s possible to find REST APIs labeled as “RESTful” as well.

RESTful APIs allow programmers to issue HTTP queries and get data in return. Data can be mapped from a cloud service to a data warehouse or vice versa using a REST API.

20. In functional programming, what exactly do you understand by the term “referential transparency”?

Referential transparency is regarded as the most important differentiating element in functional programming.  If an expression can be replaced or swapped with the corresponding value that it computes or vice versa without altering the result of the program, then that expression is said to as referentially transparent.

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21. MEAN Stack: What do you mean?

MEAN is an acronym for the following: MongoDB; ExpressJS; AngularJS; and Node.js. It’s a set of tools for creating programs that run on the web and are written in JavaScript. Though it’s a collection of technologies, all of them are grounded in the JavaScript programming language. It’s a great stack for beginners because it makes it easy to create dynamic websites and apps. Prototyping your next web app is a breeze with our free and open-source platform.

22. Do you know how to stop a bot from accessing your API if it’s available to the public?

It is technically impossible to ban data scraping in its entirety so long as the data within the API is available to the public. Yet, with the help of throttle or infrequent limiting, bot activity shall be reduced. Using rare limiting, you can cap the total amount of requests one device can make in a given time period.

An HTTP 429 Too Many Attempts error is returned whenever a client makes more than the allowed number of requests in a given time period. Because IP addresses are shared across connected devices, blacklisting the API across an entire network can be avoided if more than just the IP address is recorded.

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23. Just give me an example of a project you worked on and the tools you used to complete it.

By asking this, the interviewer can get a sense of the full stack web developer’s approach and whether or not he is adept at picking the appropriate toolset.

When discussing the rationale behind your toolkit selection, be as detailed as feasible. You need to show that you’re capable of working on both the front and back ends of a web app. It’s fine to have more experience with one aspect of development than the other, but you should demonstrate that you can handle both.

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24. Give me an example of a moment when you messed up and how you managed to correct it.

A sharp eye for detail and exactness is essential when developing. The interviewer wants to know if you pay attention to detail and can learn from your mistakes, so they might ask you this. Answer by recalling an instance when you uncovered an oversight at the office. Forget what you think you know about the situation and focus on the facts instead.

In my first few years of work, I removed a row from a database by mistake. Before sending the program off to my manager, I ran it and immediately noticed that there was a bug. Time was spent looking through the entire program for the missing code. My efficiency and accuracy have both improved after I started regularly checking my code as I went along.

25. What was the most successful implementation or debugging effort you made in the past?

The hiring manager wants to know what kinds of projects you’ve worked on in the past and how complex they were. Explicitly describe the challenges you faced and the solutions you used. You may also share any insights you gained from working through the problem.

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26. How do you upgrade yourself with the recent technical developments?

It’s important for programmers to keep up with the latest technological developments. A potential employer might ask this question as part of a screening procedure meant to gauge whether or not you are open to training and development opportunities.

Answer by considering how you now acquire knowledge of new computer-related commands and procedures. Think about options like seminars, books, online forums, and courses that lead to a certification.

Here’s an example: “I really enjoy reading up on cutting-edge technology. I currently participate in three online groups where we discuss emerging styles and trends. I keep up with developments in my field by reading a technology weekly and taking seminars. I decided last year that I wanted to learn more about back-end developments, so I enrolled in a course on the topic that was offered online. To keep my abilities current and my knowledge base expanded, I now aim to complete at least three online courses per year.”

Revise your technical expertise before attending the interview by referring to our full stack developer interview questions prepared by SLA’s experts.

Employers often look for engineers who can work across all layers of the stack since it increases their flexibility. A full-stack developer writes programs for both the client and the server. Thinking about the kinds of questions you would be asked in an interview for a full-stack developer will help you come up with engaging and well-thought-out answers and thus our full stack interview questions and answers.

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