11 Top full-stack developer interview questions

A full-stack developer is someone with knowledge of all aspects of building an application, i.e., both the front-end and back-end parts of development. As a one-man army, any full-stack developer has to write front-end code in HTML, CSS, Javascript, create APIs, create backend code in languages like PHP, Java, Python, Java, and Ruby and also work on hardware and OS. Further, understanding the design and query databases is an important part of their job.

Here is the list of 11 top full stack developer interview questions that will help you land a job.

1. What is MEAN Stack?

The MEAN stack is a JavaScript-based framework for developing web applications. The stack is named after four technologies that make up the layers of the stack:
MongoDB as the database
Express.js is the web framework
AngularJS as the frontend framework
Node.js as the server platform

2. What is the difference between a directive and a component?

Directives are added to an existing component, while components have their own view i.e., HTML and Styles.
There can only be one component in one element, while one element can have multiple directives.

3. What is the main difference between REST and GraphQL? 

GraphQL is an application layer server-side technology while REST is a software architectural style. While the former is used for executing queries with existing data, REST defines a set of constraints for creating Web services.

4. Explain the difference between “resetting” and “normalizing” CSS?

• Resetting CSS removes all the built-in browser styling. Also, there are no bug fixes in resetting.
• Normalizing CSS makes integrated browser styling in the code consistent across all browsers. It also includes bug fixes.

5. What is the difference between Nodejs, AJAX, And JQuery?

• Nodejs allows an application to run JavaScript without a browser.
• AJAX is a way for JavaScript to run a function or request data from a server without blocking an application or refreshing a page.
• JQuery is a JS library that was built to automate common JavaScript tasks like AJAX and simplify the language. 

6. What is Two-phase Commit (2PC) in the database? 

Two-phase Commit (2PC) is an atomic process that ensures that in a transaction processing system either all the databases are updated or none of them is updated. This feature enables databases to return to their pre-transaction state if an error condition occurs. Simply put, Two-phase Commit (2PC) keeps databases synchronized.

7. How can you categorize databases? 

As a full-stack developer, you need to be familiar with two or more databases.
As a document-type database, MongoDB is the most widely used for internet products. While for performance improvement, memory databases such as Redis can be used. If you are developing large-scale projects, MySQL or commercial Oracle as the back-end database is recommended.

 8. What will be the output of the following code?

var x = { foo : 1};
var output = (function() {
delete x.foo;
return x.foo;
})();
console.log(output);

The result of the above code will be the output.
output. delete operator is used to delete a property from an object. In this example, x is the object with foo as a property. We are deleting foo property from a self-invoking function and in the next call (return x.foo;) trying to reference the deleted property “foo”, this will result undefined.

9. What’s an Event Loop?

Event loop is a function that allows Node.js to perform non-blocking I/O operations even when JavaScript is single-threaded. It achieves so by offloading operations to the system kernel whenever possible.

10. How can you prevent a bot from scraping a publicly accessible API?

It is not entirely possible to prevent data scraping if the data within the API is publicly accessible. However, some measures can be taken to deter most bots.
Rate-limiting or throttling is one such measure that can prevent a specific device from making too many requests within a defined time. When the specified number of requests is reached, it will throw a ‘429 Too Many Attempts HTTP error’.
Other possible solutions can be blocking requests based on the user agent string or generating temporary “session” access tokens at the front end.

11. How rolling deployment differs from blue-green deployment?

A rolling development involves replacing an application version gradually with a newer version. In this process, system upgrade takes a while and both old and new versions will coexist without affecting user experience or functionality.
In blue-green deployment, there exist two identical production environments in parallel. The blue environment is the one that receives all the user traffic running the production environment while the green environment is the one that you will upgrade. Both these environments share the same app configurations, database, and backend. When the upgrade is done, you swap the environments, redirecting traffic from the blue to the green environment.

These questions provide an overview of what questions you can expect during an intermediate full-stack developer position interview. You are not expected to know it all, but awareness of all aspects of application development is mandatory. 

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