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Interviews / Frontend Engineering / How do you handle authentication and authorization in Next.js?

Questions

What is the difference between server-side rendering (SSR) and static site generation (SSG) in Next.js?
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What is the `_app.js` file and what is it used for in Next.js?
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What is the `_document.js` file and what is it used for in Next.js?
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How do you do data fetching in Next.js?
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How do you do routing in Next.js?
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What are API routes and how do you use them in Next.js?
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How do you do styling in Next.js?
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Your Next.js application is slow. How do you optimize its performance?
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How do you handle authentication and authorization in Next.js?
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How do you handle environment variables in Next.js?
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How do you deploy a Next.js application?
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What is middleware and how do you use it in Next.js?
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How do you handle authentication and authorization in Next.js?

practical Security Interactive Quiz Code Examples

The Scenario

You are a frontend engineer at a social media company. You are building a new application that needs to have a secure authentication and authorization system.

You need to find a way to protect your pages and API routes from unauthorized access.

The Challenge

Explain how you would handle authentication and authorization in Next.js. What are the different strategies that you would use, and what are the trade-offs between them?

Wrong Approach

A junior engineer might try to solve this problem by storing the user's session in a cookie and then checking the cookie on each request. This would work, but it would not be a very secure or scalable solution.

Right Approach

A senior engineer would know that there are several different ways to handle authentication and authorization in Next.js. They would be able to explain the pros and cons of each approach and would have a clear recommendation for which one to use in a given situation.

Step 1: Understand the Different Strategies

StrategyDescription
Cookie-basedStore the user’s session in a cookie.
Token-basedStore the user’s session in a JSON Web Token (JWT).
Third-partyUse a third-party authentication provider, such as Auth0 or Okta.

Step 2: Choose the Right Tool for the Job

Use CaseRecommended Strategy
A simple application with a few usersCookie-based
A large application with many usersToken-based
An enterprise applicationThird-party

For our use case, we should use a token-based strategy. This is because we are building a large application with many users, and we need a scalable and secure solution.

Step 3: Implement Token-based Authentication

Here’s how we can implement token-based authentication with Next.js:

1. Create an API route for logging in:

This API route will take a username and password, and it will return a JWT if the credentials are valid.

2. Store the JWT on the client:

The JWT can be stored in a cookie or in local storage.

3. Send the JWT with each request:

The JWT should be sent with each request in the Authorization header.

4. Protect pages and API routes:

We can use a higher-order component (HOC) or a middleware to protect our pages and API routes from unauthorized access.

Practice Question

You are building a simple application with a few users. Which of the following would be the most appropriate?