Top 40 Full Stack Developer Interview Questions & Answers

A complete list of the Top Full Stack Developer Interview Questions with answers and examples to quickly clear up your technical interview:

It is estimated by the U.S. Bureau of Labour Statistics that there is a substantial demand for full-stack developers from current requirements of 135,000 to increase to 853,000 by the year 2024.

Full stack developers with an earning potential of $58,040 for an entry-level position, $97,500 for mid-level, and $140,000 per year, an average pay package for experienced positions that are highly paid globally.

A full-stack developer should have mastered both client-side and server-side programming with the ability to transition from one development area to another in order to develop enterprise applications.

Full Stack developers are expected to design prototypes, develop websites from start to deployment, work on front-end architecture, build server-side business logic, manage databases, and maintain applications to resolve any anomalies. We have come up with full-stack developer interview questions often asked during technical interviews in the software industry.

Full Stack Developer Interview Questions & Answers

About Full Stack Developer

Full Stack developers develop software, databases, mobile applications, and websites to ensure they are secure, reliable, and work well.

It is essential for a Full Stack developer to be proficient in various front-end programming languages such as HTML5, CSS3, and JavaScript, and be well versed in DOM and JSON. They are expected to have a working knowledge of Git and GitHub, version control software.

A full stack developer should be good at various backend programming languages like Python, PHP, Ruby, and Java and be well versed in HTTP and REST for exchanging data between client and server via the internet and should be comfortable working with databases to manage large data and understand UI/UX design while developing prototypes and handling enterprise applications.

Top Full Stack Developer Interview Questions

Q #1) Differentiate between GET and POST.

Answer: Commonly used Hypertext Transfer Protocol (HTTP) methods are GET, PUT, POST, DELETE, and PATCH. HTTP methods GET and POST are both used on the client (browser) side to transfer data from client to server, the main difference between them is listed below:

Q #2) What are the mandatory skillsets that a full-stack developer should have?

Answer: A Full Stack developer is someone who has a good understanding of the front end, back end, browser framework, and connectivity between client and server and should be able to quickly resolve any of the development or design issues that may occur during the front end and back end integration of web-based enterprise applications.

Full stack developers are required to be well versed in skills as explained below:

HTML/CSS: Full stack developers should have expertise in creating front-end screens using HTML 5.0 and CSS 3.0 for prototype and development stack.

JavaScript/JS library: Dynamic user interface where data can be transported and requested from one page to another and all relevant actions applied on web elements such as dropdown, list, buttons, pane, canvas, menus, etc.

HTTP/REST: User interactive pages can be designed with good knowledge of HTTP methods and how to use them. REST API is applied to communicate requests with web services requested by external requests to the application server.

Web Architecture: Full stack developers essentially resolve integration issues and design pages so that these issues do not occur after implementation. User-friendly web pages that are dynamic in nature need to overcome delays due to connection issues and how these can be implemented in web and mobile applications.

Backend/Database Storage: Integration of data and requests for data from the front end with the backend and management of databases such as Oracle, MySQL, and DB2 as well as NoSQL databases like MongoDB, and Elastic Search, and good implementation skills with XML and JSON to communicate data between various applications is desired for full stack developer.

Basic Design Skills: Full-stack developers should have a working knowledge of browser compatibility issues, prototype development, UI and UX design rules, web-to-mobile migration, and scalability.

NPM: Various JS libraries and development languages such as Node.js and the concept of Node package management require an understanding of key and value pairs and their dependencies for the project.

Git and GitHub Commands: Version control software such as Git and GitHub are essential to update completed work with the build and work on an updated patch on every new release, developers should know Git and GitHub commands like add, commit, checkout, and clone.

In addition, Full Stack developers will have to lead the team of developers and communicate with various stakeholders like the project manager, design head, product team, and engineering head. It is essential to have soft skills such as communication, negotiation, and conflict resolution.

Q #3) Explain RESTful API and its use.

Answer: Secured information/data exchange between two different applications using HTTP over the internet requires an interface known as RESTful API that offers reliable, scalable, high-performing, and data-intensive communication.

The client (browser) will contact the server using the API and will request resources for the following steps:

• A request from the client will be sent to the server in a way the server can understand.
• After confirming with the client and their authentication server receives the request to process it internally
• The response from the server is sent to the client that contains information on the client if the request was successful along with the client’s requested information.

Q #4) Describe a callback in JavaScript.

Answer: Callback in Javascript can be described as a function passed to another function in the form of an argument.

Callback is used after the completion of an asynchronous operation to continue code execution. Callback is used to execute a code in response to an event such as the click of a button or clicking a particular key on a keyboard.

Q #5) What are popular stacks?

Answer: The stacks popularly used in the software industries are MEAN, MERN, MEVN, LAMP, Serverless Stack, and Flutter for the Web.

• MEAN: M for MongoDB, E for Express.js, A for AngularJS and N for Node.js. It is an open-source, free, and complete JavaScript stack. It is extensible, scalable, and flexible and can be deployed on the server that it includes. MEAN stack can be useful to include calendars, mapping, location finding, and creating newsgroups sites
• MERN: M for MongoDB, E for Express.js, R for React and N for Node.js. React uses JSX (modified JavaScript) and virtual DOM, and the changes can be done with ease. It is easy to build single-page applications with interactive User interfaces with React framework.
• MEVN: Similar to MEAN with front-end framework, AngularJS replaced with Vue.js, is lightweight compared to Angular. Vue.js has out-of-the-box features and is extensible to third-party services.
• LAMP: L for Linux, A for Apache, M for MySQL, and P for PHP, LAMP is a completely open-source stack that is used by famous CMS software like WordPress and Drupal. Linux can be replaced with Microsoft Windows to form WAMP or MAC OS to form MAMP. PHP can be replaced with Perl or Python.
• Serverless Stack: For simpler infrastructure management Serverless platform offer tools and services. AWS Lambda is a serverless platform and Google Cloud is a serverless computing services provider.
• Flutter for Web: Used for cross-platform development with the same User Interface and business logic across all platforms. Adding new features, bug fixing, and building user interfaces is quick.

Q #6) What is included in client-side programming?

Answer: The client-side components include help files, property files, jar or class files (for Java-based development), specification files, image files, CSS and JavaScript files, and Java API.

The front-end development requires a full stack developer to be proficient in HTML, CSS, JavaScript, HTML DOM, JavaScript libraries like JQuery, Angular, React, XML, and JSON, good understanding of HTTP protocol, and handle front page look and feel for multiple browsers.

Q #7) What is included in server-side programming?

Answer: Full Stack developers should be comfortable on at least one of the stacks – like LAMP, LEMP, MEAN, MERN, MEVN, which covers MongoDB, Express, Angular JS, Node.js, Python, Ruby, Linux, MySQL, PHP, SQLite, Rails and of course JavaScript.

The database can be relational like MySQL or NoSQL like MongoDB.

Good knowledge of working with database objects such as schemas, tables, views, indexes, triggers, sequences, and stored procedures, etc. as well as NoSQL or document databases such as express, MongoDB, or elastic Search, working knowledge of HTTP request/response and developing Web services for the application.

Q #8) List some popular Full Stack tools.

Answer: Following are some of the popular tools used for Full Stack development:

• Backbone
• CodePen
• Electron
• Visual Studio Code
• TypeScript
• WebStorm
• GitHub
• Slack

Q #9) Describe Pair Programming in depth.

Answer: In an Agile software development environment two developers work together on a particular code where one of them writes a code whereas another one reviews each line of the code. Each of them exchanges their role frequently, which is known as pair programming.

The pair programming over individual programmers working on the code has the advantage of the resultant code with fewer defects and reduces development time, both of these developers work as a backup for the business logic used in the code, in addition, their coding skills and prior experience offer more solutions to the problems faced during coding.

The combination can be both of the programmers can be experts (expert-expert), one of them in the pair is new (expert-novice) or both are new to coding (novice-novice).

Q #10) What is Cross-Origin Resource Sharing (CORS)?

Answer: A typical web page may have images, videos, style sheets, scripts, and iframes embedded in it. Based on the same-origin policy, JavaScript code is prevented from accessing elements from a domain that is not the same but different from the launching domain.

These restricted resources allow requests from domains outside the domain from their launch domain that was initially served. The mechanism is known as Cross-Origin Resource Sharing – CORS.

It extends flexibility to the Same Origin Policy (SOP) and allows controlled access to resources outside of the domain from where the request was initiated. Cross-origin resource sharing has vulnerabilities as well if not configured properly.

Q #11) List the ways to improve website load time and performance.

Answer: It is essential that your web pages load quickly to prevent bounce rates and increase the engagement of people visiting your website pages. The bounce rate is the percentage of people that land on your page but leave without clicking or visiting any of the child pages.

You can follow these few tips to improve performance and website load time:

• Always select reliable, high-performance hosting software like WordPress, Jumla, Drupal to host your website.
• Compressing images that are large in size can take time while loading the web page by using image compressing utilities like tinypng.com or Attrock.
• Optimize your page redirects to the minimum as it involves the HTTP request-response process.
• The caching of web pages can lower time to the first byte, Time to first byte (TTFB) – which is a measure of the time-lapse of the browser before receiving the initial byte of data in the form of information from the server.
• Asynchronous loading allows multiple loading of JavaScript and CSS files at the same time.
• Remove unused CSS and script files by optimizing CSS, JavaScript, and HTML code. Use minimal plugins.
• Selecting Content Delivery Network (CDN) can be leveraged to improve the speed at which web pages will be loaded.
• HTTP requests should be minimal and there should be a cache at the browser level.

Q #12) List the differences between Abstract class and Interface in Java.

Answer: During the declaration of abstract methods in Java, an Abstract class or Interface can be used to achieve abstraction. Interface or Abstract class cannot be instantiated – interfaces can be instantiated whereas an abstract class can be sub-classed.

The differences between Interface and abstract classes in Java are listed below:

Q #13) What is RESTful API?

Answer: An application program interface built on REST architecture for secured, scalable and lightweight services to communicate between two applications, transfer data, and utilize web services using hyper-text transfer protocol.

Various web and mobile-based applications like LinkedIn, Twitter, Facebook, Google, and Amazon use REST API for their users to communicate and access their web services and share the information their users are requesting. Online flight reservations, weather forecasts, cloud computing, and microservices are a few uses of RESTful API.

Q #14) What are the three main design patterns?

Answer: A reusable solution to common problems occurring in software design is known as a design pattern – which showcases interaction and relation between objects or classes. This pattern helps to build reusable, maintainable, and flexible code.

There are mainly three design patterns namely – structural, creational, and behavioral. Class composition and structure refer to structural design patterns and this pattern is used to improve the functionality of classes without any changes in their composition.

Creational design patterns, also known as class or object creational patterns, are used for instantiating the class. Based on the communication between one class and another class, a behavioral design pattern is designed.

Q #15) Difference between GraphQL and REST.

Answer: GraphQL is server-side technology built on the application layer that uses the execution of queries for existing data, REST is an architectural style that configures a set of constraints to create web services. REST is arranged in the form of endpoints whereas GraphQL is organized in the form of a schema.

Q #16) Explain continuous integration.

Answer: The main duty of the DevOps team is to integrate code from multiple developers during continuous development. Various codes should seamlessly get integrated and merged into a central repository where the code is built, tested for any errors, and then run.

Continuous integration is a process of automatically integrating code received in a central repository continuously built, tested, and runs creating applications to release test and development builds. Git and GitHub are some of the commonly used tools for continuous integration.

Q #17) Why MongoDB is the preferred database for full-stack development?

Answer: MongoDB is a NoSQL database with no enforcement of relations or schema. Connecting MongoDB with Express and node is easy, whereas Express.js is the application framework on the server side making it easy to map server-side functions to URLs and wrap HTTP requests and responses.

Node.js is a JavaScript library that is cross-platform and an open-source runtime environment used for back-end API services and websites that are deployed on non-blocking event-driven servers. Some of the other databases used in Full Stack development are MySQL, PostgreSQL, Microsoft SQL Server, Redis, ElasticSearch, Oracle, DynamoDB, and MariaDB.

Q #18) What are the advantages of using bootstrap?

Answer: Bootstrap is mobile-first, open-source CSS framework used to develop websites and applications. The latest version of Bootstrap is version 5 which is compatible with all browsers. CSS is responsive and adjusts to any screen size of a desktop, mobile, or tablet.

Unlike previous versions, Bootstrap 5 has switched to JavaScript. Designing a prototype of an application becomes quick with the Bootstrap framework.

Q #19) Explain the common goals for domain-driven design.

Answer: Domain-driven design goals are:

• Core domain and logic are the primary focus of the application.
• Models have a complex design based on the domain.
• Domain problems are addressed by the association of technical and domain experts to fine-tune solutions iteratively.
• The names of classes, methods, and variables are defined based on the domain. For example, a loan processing application will have a class name like LoanProcessor, a method name like calculateInterest(), principalAmt(), and variables like loan type, rateofInterest, duration, etc.

Q #20) Define data migration.

Answer: Migration of data is a process involving preparing, selecting, and moving data from one source to another source, it also means moving on-premise applications with data and/or infrastructure to cloud-based storage.

There are three types of migration – storage, cloud, and application. All of this migration involves steps like extraction, transformation, and loading of data.

Q #21) Explain how real-time messaging works.

Answer: The mechanism of distributing messages in real-time – instantly on the occurrence of events. Real-time messaging is utilized in handling distributed autonomous devices used in the monitoring of industrial processes, infrastructure management, and environment control.

HTTP Long Polling, Web Sockets, and XMPP are real-time messaging protocols that support an online user’s or device’s presence.

Q #22) Explain Design patterns used in Microservices.

Answer: Microservices is an approach in software engineering that concentrates on dividing software applications into modules that have a single function and an interface that is well-defined. It is an architectural pattern that is service oriented where small and independent service units are built as a group.

Various design patterns for microservices are:

• API Gateway
• Asynchronous Messaging
• Aggregator
• Branch
• Circuit Breaker
• Chained or Chain of Responsibility
• Command Query Responsibility Segregator
• Decomposition
• Database or Shared Data
• Event Sourcing

Q #23) What are alternatives for AngularJS?

Answer: AngularJS is an open-source framework that helps in creating dynamic web applications with user-interactive components.

Due to its flexibility, simplicity, and effectiveness, it has become the preferred framework while creating Full Stack interactive web applications. Like all major open-source software, community support for AngularJS has been discontinued since 31^st December 2021.

The alternatives for AngularJS are Angular, React.js, Aurelia, Ember.js, Backbone.js, Lit, Meteor, Knockout, Vue.js, and Riot.js.

Q #24) What is CRUD stands for in HTTP  request?

Answer: In the HTTP request, C is Create corresponds to the Post request, R is Read corresponds to the Get request, U is Update that corresponds to Patch/Put request, and D is Delete for the Delete request method.

Post requests are to create or update a resource by sending a request or data to a server and parameters are seen in the message body whereas in getting a request the parameters requested during the request are appended in the URL string.

Q #25) What JavaScript task runners use in Full Stack development?

Answer: Various computer processes that require manual intervention can be automated with the help of JavaScript task runners namely Grunt and Gulp. These structurally identical command line tools essentially help in optimizing a workflow. Code verification and compilation of code and unit testing are some of the processes executed using task runner.

Q #26) Define dependency injection.

Answer: It is a design pattern similar to that of inversion of control form, where a function or object receives other functions or objects they are dependent on. With dependency injection, implicit dependencies are made explicit and solve the following problems

• Creating dependent classes independent from object creation.
• Support for different configurations for objects and applications they use.
• Changes in code behavior without any direct modification in a code.

There are three categories of dependency injections – property injection, method injection, and constructor injection. Developers use dependency injections to design testable code and write unit tests.

Q #27) Explain the purpose of the Observer pattern.

Answer: The observer pattern is applied with a focus on the object state and gets a notification in case of any changes in the state. The pattern supports interacting objects that are loosely coupled.

With an Observer pattern, data can be sent to other objects without any modification in the observer or subject class. It allows the addition or removal of observers without changes in subjects or observers at any point needed. The observer pattern is categorized in behavioral patterns as it allows changes in observers and subjects independently.

Q #28) Describe GraphQL

Answer: GraphQL is a server-side runtime and query language for application programming interfaces that offer only the specific data clients are looking for. It is mainly used for remote communication between client and server.

GraphQL is strongly typed, suitable for microservices and complex software applications help to retrieve exact and specific data in a single request. This allows users to create requests to retrieve data from multiple sources of data in a single API call.

GraphQL is ideally used for applications that have a composite pattern to retrieve nested data, or from multiple different API storages faster. It is used for applications specifically designed for smartphones, mobiles, and IoT devices that are sensitive to bandwidth usage.

Q #29) Explain event bubbling and event capturing in JavaScript DOM.

Answer: Event bubbling is a process that starts with an event reaction to an element followed by event handlers, parents, and other ancestors working on the element. Event capturing on the other hand is the opposite of event bubbling, where the event begins at the parent element and then to the child of that parent.

Event bubbling is the default behavior of an event, to prevent event bubbling, we can use the stopPropagation method. Both events capturing and bubbling is part of event propagation.

Q #30) What are Dockers?

Answer: A standard software unit that contains code and all its dependencies packaged together is known as a container so that applications can reliably and quickly run across various computing environments. Docker is a lightweight, executable, and standalone pack that contains code, system tools, settings, libraries, and runtime.

Regardless of the difference between staging and development instances, containers like Docker ensure the working of applications seamlessly. Dockers are known as cgroup and namespaces in Linux and can be implemented in Linux, Windows, Data Centers, Cloud, and Serverless environments.

Q #31) Compare AMD with CommonJS.

Answer: AMD is asynchronous, flexible, and can run without building in the browser. The AMD path dependency listings and resolution are simplified with the help of path aliases and some advanced settings in configuration. It can load other than JavaScript.

The listing of dependencies in AMD is in the same location making it easy to find out about dependencies. AMD is adopted by JS libraries like JQuery, Dojo, and Mootools. It also offers lazy-load scripts if required. CommonJS requires loading from module repositories like npm.

Access to CommonJS is possible via the context of Node.js application. Dependencies like npm, nodejs, and yeoman should be pre-installed in order to use CommonJS module. CommonJS modules are loaded synchronously.

Q #32) Describe the ways to find memory leaks in Java.

Answer: Objects that remain unused occupy memory space resulting in memory leaks. In Java, Garbage Collection removes such objects and frees up space.

Memory leaks can occur due to various reasons such as the use of session objects extensively, insertion of objects without deletion of collection objects, Unbound cache, listener methods that have been left un-invoked, a customized data structure that is poorly written in code, and frequent page swapping related to the operating system.

Memory leaks in Java can be identified by following the ways:

• Using Memory Profilers and tools like JProfiler, YourKit, and Java VisualVM.
• Adding in JVM configuration (-verbose:gc) enabling verbose garbage collection.
• Heap dumps are used to capture snapshots of heap memory for applications built in Java.

Q #33) How to prevent deadlock in Java?

Answer: A deadlock is a programming instance where two or more threads are forever blocked. Deadlock can be avoided by implementing any of the following

• Avoid Nested Locks, Unnecessary Locks and
• Using Thread.join().

Q #34) Explain why the map is not a member of the Java collection interface.

Answer: A map is a data structure that can store pairs of key-value having unique keys. Java Collection is extended to List, Set, and Queue. The map is not a member of the collection interface as it is a collection of key-value pairs whereas list, set and queue are collections of similar objects.

The map uses the put function and uses key and values as their parameters whereas the list, set and queue uses add function to add elements. Maps use keys to iterate (navigate) over which is Set and values as a Collection.

Q #35) What is an application server?

Answer: Server where software applications and services for organizations are installed, operated, or hosted by end users or organizations using these applications. Application servers are mainly of three types – Tier 1, Tier 2, and Tier 3.

Tier 1 server has all the application elements – user interface, middleware, and back-end installed in one place. Tier 2 servers have two separate layers – client and server, dividing application logic, data, and processing between client and server. Tier 3 server has a presentation layer, application logic on a separate tier, and data processing layers on a separate server.

Examples of the application servers are WebSphere, JBoss, WebLogic, JRun, Glassfish.

Q #36) What do you mean by IPS in data theft prevention?

Answer: The protection of data and prevention of its theft by investigating network data flow to detect and identify network vulnerability and prevent malicious activities that result in unauthorized data access or theft is known as IPS. IPS is of various types – anomaly-based, protocol-based, policy-based, and signature-based.

Q #37) What are the latest trends in full stack development?

Answer: Knowledge of the latest and upcoming technologies like Artificial Intelligence, the Internet of Things, Blockchain, Machine Learning, and progressive web applications is what is required in a candidate applying for the post of full stack developer.

As per the latest trends, evaluation of compatible extensions and programming using improved JavaScript and their libraries. There is a rise in demand for experience using Vue.JS functions, mobile and real-time web applications, REST API, and web services.

Q #38) What are the configuration management tools?

Answer: DevOps team uses various IT configuration automation tools such as Ansible, Chef, and Puppet for continuous delivery, infrastructure, orchestration, and integration of configuration and security compliance.

These tools help system administrators work with the operations team during the integration, installation, and configuration of multitier applications in the development, test, and production environment.

Q #39) Explain container orchestration and list the tools used.

Answer: Containers in software industries are used to store binaries, libraries, configuration files, and executables that are essential to run the application. Container orchestration helps automate the process of deployment, scaling, networking, and managing these containers.

Various tools used for container orchestration are Docker Swarm, Kubernetes, and Apache Mesos.

Q #40) What are the various testing you will perform on web applications using full stack?

Answer: Following is the testing we will perform on the web application

• Accessibility testing
• Performance testing
• Exploratory manual testing
• Automated functional testing
• Security Testing
• Data testing
• Cross-functional/ Integration testing
• Mobile testing

Conclusion

We have come to the end of this tutorial on Full Stack Developer interview questions. Full Stack developers should have experience developing applications using any one of the stacks from MEAN, MERN, MEVN, or LAMP.

It is expected that a Full Stack developer has excellent work experience in document databases like MongoDB, servers like Node.js, and scripting languages like JavaScript, JQuery, Vue, or Angular to manage browsers.