19 Web Performance Interview Questions and Answers

As the demand for faster and more responsive web applications increases, so does the need for developers with the skills to optimize web performance. When interviewing for a position that requires web performance skills, be prepared to answer questions about your experience and knowledge in this area. In this article, we review some common web performance interview questions and provide tips on how to answer them.

Web Performance Interview Questions and Answers

Here are 19 commonly asked Web Performance interview questions and answers to prepare you for your interview:

1. What are the main factors that affect web page performance?

The main factors that affect web page performance are the size of the page, the number of requests, the number of resources, the type of resources, and the server response time.

2. How do you measure and track web performance using Google Analytics?

You can measure web performance using Google Analytics by tracking the page load time, the time to first byte, and the time to first interaction. To track the page load time, you will need to set up an event tracking code on your website. To track the time to first byte, you will need to use the PageSpeed Insights tool. To track the time to first interaction, you will need to use the User Timing API.

3. Can you explain what a waterfall chart is, in context with web performance?

A waterfall chart is a type of graph that is used to visualize the different steps that occur during a web page load. Each step is represented by a bar, and the bars are arranged in the order that the steps occur. This allows you to see at a glance where the longest delays are occurring, and can help you to identify bottlenecks in the loading process.

4. Can you explain how caching works on the server-side?

When a user visits a website, their browser will send a request to the server for the desired page. The server will then check its cache to see if it has a copy of that page. If it does, it will send the cached version to the user. If it does not, it will generate the page and send it to the user. The next time that same user visits the site, the server will again check its cache. This time, it will find a copy of the page and can send it to the user without having to generate it again, which saves time.

5. What are some ways to load JavaScript asynchronously?

One way to load JavaScript asynchronously is to use the async attribute on the script tag. This will tell the browser to continue loading the page while the script is being downloaded and executed. Another way to load JavaScript asynchronously is to use a dynamic script tag. This approach uses a JavaScript function to create a script tag and append it to the page. The browser will then load and execute the script.

6. Can you give me an example of where I can use gzip compression to improve website performance?

Gzip compression can be used to improve website performance by reducing the size of files that are transferred between the server and the client. This can reduce the amount of time that it takes to load a page, as well as reduce the amount of bandwidth that is used.

7. Is it possible to cache CSS files for faster loading times? If yes, then how?

Yes, it is possible to cache CSS files for faster loading times. This can be done by setting up a server-side cache, which will store a copy of the CSS file and serve it up to visitors when they request it. Alternatively, you can use a client-side cache, which will store a copy of the CSS file on the user’s computer and serve it up from there when requested.

8. Are there any negative side effects of enabling HTTP Keep Alive?

One potential negative side effect of enabling HTTP Keep Alive is that it can lead to increased latency if not configured properly. If there are too many persistent connections, it can actually start to bog down the server. Another downside is that it can make it more difficult to debug connection issues since all of the connections are persistent.

9. What are the best practices you should follow when designing images to be used on your site?

When it comes to images, there are a few things you should keep in mind to ensure optimal performance. First, try to use images that are compressed as much as possible without sacrificing quality. Second, make sure that your images are sized appropriately for the location in which they will be used. And finally, try to use a caching system to ensure that your images are loaded quickly and efficiently.

10. What is the difference between Sharding and GZip Compression? Which one would you recommend in certain situations?

Sharding is a process of splitting up data across multiple servers in order to improve performance. GZip Compression is a process of compressing data in order to reduce the amount of data that needs to be transferred. In general, I would recommend sharding over GZip compression because sharding can provide a more significant performance boost. However, GZip compression can be useful in situations where data needs to be transferred over a slow connection.

11. What’s the impact of browser testing on web performance?

Browser testing can have a significant impact on web performance, as it can help to identify and fix potential issues that could slow down a website. In addition, browser testing can also help to ensure that a website is compatible with the most popular browsers, which can help to improve its overall reach and accessibility.

12. What are some ways to make frontend code more efficient?

There are a few different ways to make frontend code more efficient:

1. Use a CSS preprocessor like Sass or Less to help reduce the size of your CSS files.
2. Use a JavaScript minifier like UglifyJS to help reduce the size of your JavaScript files.
3. Use a build tool like Grunt or Gulp to help automate tasks like minification, concatenation, and linting.
4. Use a frontend framework like AngularJS or ReactJS to help structure your code in a more efficient way.
5. Use a performance monitoring tool like New Relic to help identify areas of your code that could be improved.

13. What tools or methods do you use to check if your Javascript/CSS is minified?

There are a few different ways to check if your Javascript/CSS is minified. One way is to use a tool like JSLint or CSSLint. These tools will analyze your code and look for any unnecessary characters or whitespace. Another way is to simply open up your code in a text editor and look for any extra characters. Finally, you can also use online tools like MinifyCode.com which will minify your code for you and then show you the difference in size.

14. How do you optimize your HTML markup to reduce page size?

There are a few different ways to optimize your HTML markup to reduce page size. One way is to minify your HTML code, which basically means removing all unnecessary characters from your code, such as whitespace, comments, and so on. This can often reduce your code by a significant amount, and can be easily done using a tool like HTMLMinifier.

Another way to reduce page size is to use a CSS preprocessor like Less or Sass to compress your CSS code. This can often reduce your CSS code by a significant amount, and can also help you to avoid duplicate code.

Finally, you can also use a tool like Gzip to compress your HTML code before it is sent to the browser. This can often reduce the size of your HTML code by up to 70%, and can make your pages load much faster.

15. What is the process involved in optimizing website content delivery across multiple devices?

The process of optimizing website content delivery across multiple devices generally involves four steps:

1. Identifying the devices that will be accessing the site.
2. Identifying the content that needs to be delivered to each device.
3. Modifying the website to deliver the appropriate content to each device.
4. Testing the website to ensure that the content is being delivered correctly.

16. What are some ways to speed up data transmission over networks?

There are a few ways to speed up data transmission over networks:

1. Use a faster network protocol: Some protocols are faster than others. For example, using a 10 Gigabit Ethernet protocol will be faster than using a 100 Megabit Ethernet protocol.

2. Use a faster network: If you are using a network that is slower than your computer’s capabilities, upgrading to a faster network will speed up data transmission.

3. Use a faster computer: If your computer is slower than the network you are using, upgrading to a faster computer will speed up data transmission.

4. Use compression: Compressing data before sending it over a network will reduce the amount of time it takes to transmit the data.

17. What are the advantages of progressive rendering?

Progressive rendering is a technique used to improve the performance of web pages by loading content incrementally. The advantage of this approach is that it allows the user to begin interacting with the page sooner, while the rest of the content is still loading in the background. This can improve the overall user experience, especially on slow connections.

18. Can you explain how image sprites work?

Image sprites are a way to improve web performance by reducing the number of HTTP requests that need to be made when loading a page. Instead of having each image be a separate file, image sprites combine multiple images into a single file. This means that the browser only needs to make a single request to load all of the images on the page, which can speed up page loading times.

19. What are some ways to compress JavaScript to increase performance?

There are a few ways to compress JavaScript in order to increase performance. One way is to use a minifier, which is a tool that will remove all unnecessary characters from the code, such as whitespace and comments. Another way is to use a compressor, which will actually compress the code itself, making it smaller and thus faster to download and parse.