The Vital Guide to Interviewing Web Developers

This guide offers a sampling of effective questions to help evaluate the breadth and depth of a candidate's mastery of web development, including client-side, server-side, transport, and database related topics.

Before we embark on the journey of identifying world-class web developers, we must first define exactly what we mean by “web development”. Are we referring to the development of a web site? Or the development of a web service? Or the development of a complex web-based application? The truth is that web development is an extremely broad term that can legitimately encompass any or all of the above. Accordingly, this guide touches on multiple aspects of web development, some or all of which will be relevant to the specific context in which you may be looking to hire.

This guide intentionally focuses on the conceptual and architectural underpinnings of web development, rather than delving into the specifics of any specific web technologies (such as JavaScript, Ruby on Rails, PHP, and so on). Accordingly, this guide presents “technology-agnostic” web developer interview questions relating to:

• Client-side (browser-based development)
• Server-side
• Transport
• Database

Admittedly, doing justice to many of the topics herein would warrant posts of their own. Nonetheless, this guide strives to provide at least a meaningful overview of key issues and topics relating to web development in which a highly-experienced web developer can be expected to be well-versed.

Client-side (browser-based development)

Browser-based development presents numerous unique challenges to the developer, ranging from cross-browser anomalies, to sandbox limitations, to diverse performance characteristics across a wide array of client platforms and devices. Adept client-side web developers will be highly skilled at navigating these obstacles.

Q: Discuss at least three areas of focus on the client side to help reduce page load time.

Performance is central to a user’s experience with any application. Users have become increasingly intolerant of slow page load times and, knowing this, the large search engines actually quantify that time for each of the pages that their bots crawl.

Making the initial page request, getting the initial response contents of a page to the client, parsing that content and making subsequent requests for resource items (which in themselves are a round trip to and from the server), and then running any JavaScript can all contribute to page load time.

There are in fact numerous techniques to employ and areas to focus on to help improve page load time. Here are just a few examples:

• Avoid “render blocking”. When the browser’s parser engine encounters a tag in the HTML that accesses some external resource (such as a <script>, <image>, <iframe>, etc.) the engine pauses to wait for that resource to download fully to the client before continuing. Even worse, in the case of a <script> tag with a src attribute, the browser will also execute that script before it moves on to process the rest of the page. This becomes particularly problematic when that script may subsequently make another request. Most browsers provide an async attribute that you can add to those tags to avoid this type of blocking. Another strategy is to identify resources that you can delay loading until they are actually needed.
• Optimize images. Probably the largest resources you will load into a page are your images. Optimizing them for transport can prove to be very beneficial, as appropriate sizing can substantially reduce page load times. For example, don’t use a 600px by 400px image for a 120px by 80px thumbnail. It’s also helpful to pick the best compression format and to turn off certain format features.
• Minimize round-trip requests. The round-trip of retrieving resources (images, etc.) from the server can be a huge problem for page load times. Since the fewer requests a page makes, the faster it will be, one technique to help performance is to combine resources together into fewer requests where possible. For example, non-user generated images are a prime candidate here. A round-trip to the server just to retrieve a single 16x16 smiley face emoticon, for example, is extremely inefficient.

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by Demir Selmanovic via SitePoint