Toptal Engineering Blog

The Toptal Engineering Blog is a hub for in-depth development tutorials and new technology announcements created by professional freelance software engineers in the Toptal network.
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An Introduction to Mocking in Python

More often than not, the software we write directly interacts with what we would label as “dirty” services. In layman’s terms: services that are crucial to our application, but whose interactions have intended but undesired side-effects—that is, undesired in the context of an autonomous test run.

For example: perhaps we’re writing a social app and want to test out our new ‘Post to Facebook feature’, but don’t want to actually post to Facebook every time we run our test suite.

The Python unittest library includes a subpackage named unittest.mock—or if you declare it as a dependency, simply mock—which provides extremely powerful and useful means by which to mock and stub out these undesired side-effects.

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Anti-Patterns in Telecommuting

As a veteran telecommuter through multiple jobs in my career, I have witnessed and experienced the many joys of being a remote worker. As for the horror stories, I have more than a few I could tell. With a bit of artistic inclination and a talent for mathematics, I also have a fascination with patterns: design patterns, architectural patterns, behavioral patterns, social patterns, weather patterns—all sorts of patterns!

When I first encountered anti-patterns, I discovered a trove of wisdom I wish I had known before I had learned the hard way. Anti-patterns are recognizable repeated patterns that contribute significantly to failure. For example, the manager that keeps interrupting the employee in order to see if the employee is getting any work done is engaging in an anti-pattern that serves to prevent the employee from getting any work done!

Based on my own experiences and experiences of friends and co-workers, I am assembling descriptions of anti-patterns related to telecommuting.

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Great Developers Know When and How To Refactor Rails Code

If it ain’t broke, don’t fix it.

It’s a well known phrase, but as we know, most of the human technological progress was made by people who decided to fix what isn’t broken. Especially in the software industry one could argue that most of what we do is fixing what isn’t broken.

Fixing functionality, improving the UI, improving speed and memory efficiency, adding features: these are all activities for which it is easy to see if they are worth doing, and then we argue for or against spending our time on them. However, there is an activity, which for the most part falls into a gray area: refactoring, and especially large scale refactoring.

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With a Filter Bypass and Some Hexadecimal, Hacked Credit Card Numbers Are Still, Still Google-able

In 2007, Bennett Haselton revealed a minor hack with major implications: querying ranges of numbers on Google would return pages of sensitive information, including Credit Card numbers, Social Security numbers, and more. While Haselton’s hack was addressed and patched, I was able to tweak his original technique to bypass Google’s filter and return the same old dangerous results.

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A Step-by-Step Tutorial for Your First AngularJS App

If you haven’t tried AngularJS yet, you’re missing out. The framework consists of a tightly integrated toolset that will help you build well structured, rich client-side applications in a modular fashion—with less code and more flexibility.

One of the reasons I love working with AngularJS is because of its flexibility regarding server communication. Like most JavaScript MVC frameworks, it lets you work with any server-side technology as long as it can serve your app through a RESTful web API. But Angular also provides services on top of XHR that dramatically simplify your code and allow you to abstract API calls into reusable services. As a result, you can move your model and business logic to the front-end and build back-end agnostic web apps. In this post, we’ll do just that, one step at a time.

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Why Writing Software Design Documents Matters

Congratulations, you’re an independent developer. From beginnings working maybe as a tester you’ve progressed to a team developer, then a senior developer, and now you’ve made another leap, the biggest of them all, to working directly with clients.

But where the other transitions were linear, this last one was exponential. While in the past you got your marching orders from an employer that worked with clients or was itself in the software business, now all those responsibilities that were once distributed between expert-testing, program management, etc., are all yours. And now you’re working with clients who are not in the software business; they’re in another business that needs a piece of software, and they don’t have a clear and precise vision of what they want from you. This is a far greater challenge than it appears.

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SQL Database Performance Tuning for Developers

Database tuning can be an incredibly difficult task, particularly when working with large-scale data where even the most minor change can have a dramatic (positive or negative) impact on performance.

In mid-sized and large companies, most database tuning will be handled by a Database Administrator (DBA). But believe me, there are plenty of developers out there who have to perform DBA-like tasks. Further, in many of the companies I’ve seen that do have DBAs, they often struggle to work well with developers—the positions simply require different modes of problem solving, which can lead to disagreement among coworkers.

In this article, I’d like to both provide developers with some developer-side database tuning tips and explain how developers and DBAs can work together effectively.

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Hunting Memory Leaks in Java

Inexperienced programmers often think that Java’s automatic garbage collection frees them from the burden of memory management. This is a common misperception: while the garbage collector does its best, it’s entirely possible for even the best programmer to fall prey to crippling memory leaks.

In this post, I’ll explain how and why memory leaks occur in Java and outline an approach for detecting such leaks with the help of a visual interface.

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Why Are There So Many Pythons? A Python Implementation Comparison

Python is amazing.

Surprisingly, that’s a fairly ambiguous statement. What do I mean by ‘Python’? Do I mean Python the abstract interface? Do I mean CPython, the common Python implementation? Or do I mean something else entirely? Maybe I’m obliquely referring to Jython, or IronPython, or PyPy. Or maybe I’ve really gone off the deep end and I’m talking about RPython or RubyPython (which are very, very different things).

While the technologies mentioned above are commonly-named and commonly-referenced, some of them serve completely different purposes (or at least operate in completely different ways). In this post, I’ll start from scratch and move through the various Python implementations, concluding with a thorough introduction to PyPy, which I believe is the future of the language.

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The Trie: A Neglected Data Structure

From the very first days in our lives as programmers, we’ve all dealt with data structures: Arrays, linked lists, trees, sets, stacks and queues are our everyday companions, and the experienced programmer knows when and why to use them.

In this article we’ll see how an oft-neglected data structure, the trie, really shines in application domains with specific features, like word games.

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Scaling Play! to Thousands of Concurrent Requests

Web Developers often fail to consider the consequences of thousands of users accessing our applications at the same time. Perhaps it’s because we love to rapidly prototype; perhaps it’s because testing such scenarios is simply hard.

Regardless, I’m going to argue that ignoring scalability is not as bad as it sounds—if you use the proper set of tools and follow good development practices. In this case: the Play! framework and the Scala language.

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Forex Algorithmic Trading: A Practical Tale for Engineers

A few years ago, driven by my curiosity, I took my first steps into the world of Forex by creating a demo account and playing out simulations (with fake money) using the Meta Trader 4 trading platform.

After a week of ‘trading’, I’d almost doubled my ‘money’. Spurred on by my own success, I dug deeper and eventually signed up for a number of forums. Soon, I was spending hours reading about trading systems (i.e., rule sets that determine whether you should buy or sell), custom indicators, market moods, and more.

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What are the Benefits of Ruby on Rails? After Two Decades of Programming, I Use Rails

Sometimes I hear people complaining about their clients, saying that they insist on using Rails, that they’ve had too much Kool Aid. If they are recruiters, they almost feel sick in the stomach from perspective of having to find yet another ROR primadona. From the programmers point of view it sometimes looks like clients don’t have a clue. However, I believe most clients know their options just fine and they still decide to go with Rails.

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Build Dumb, Refactor Smart: How to Massage Problems Out of Ruby on Rails Code

Sometimes, clients give us feature requests that we really don’t like. It’s not that we don’t like our clients, we love our clients. It’s not that we don’t like the feature, most client-requested features are aligned perfectly with their business goals and income. Sometimes, the reason we don’t like a feature request is that the easiest way to solve it is to write bad code, and we don’t have an Elegant Solution on the top of our heads. This will throw many of us on fruitless searches through RubyToolbox, github, developer blogs, and stackoverflow looking for a gem or plugin or example code that will make us feel better about ourselves.

Well, I’m here to tell you, it’s okay to write bad code. Sometimes, bad code is easier to refactor into beautiful code than a poorly thought out solution implemented under a time-crunch.

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Why The Hell Would I Use Node.js? A Case-by-Case Tutorial

Node.js shines in real-time web applications employing push technology over websockets. What is so revolutionary about that? Well, after over 20 years of stateless-web based on the stateless request-response paradigm, we finally have web applications with real-time, two-way connections, where both the client and server can initiate communication, allowing them to exchange data freely. This is in stark contrast to the typical web response paradigm, where the client always initiates communication. Additionally, it’s all based on the open web stack (HTML, CSS and JS) running over the standard port 80.

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How a Single Front-End Engineer Can Replace a Team of Two

Demand within the web design scene today has changed over the past few years: designers with front-end skills, and front-end developers with design skills, are more and more in demand. Yes, you could argue that the jobs are completely different—and maybe you straight-up don’t like one of them—but truth be told, in my six years as a freelance web developer and twelve years as a designer, I’ve learned that it’s much harder to get by as just a web designer or just a front-end developer.

Wearing both hats has a lot of advantages: from a professional perspective alone, you can find work more easily and charge a higher rate because you’re bringing more to the table.

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The Ultimate Remote Team Culture

At Toptal, we’re building a software product that aims to revolutionize team creation, contracting, and human resources. Our team is completely distributed: we have no office, and we work from all around the globe. And when I say “all around the globe”, I mean “all around the globe”: our internal staff consists of nearly 50 full-time individuals from Brazil, USA, Russia, Argentina, Czech Republic, Ukraine, Hungary, and more. This includes engineers, designers, recruiters, sales, and executives.

We all work from home, and we’re good at it: we’ve had countless Skype sessions, code reviews, feature iterations—all components in building a great product. We work hard, and we’ve been at it with as much fervor and energy as ever.

Earlier this year, we decided it was time to bring everyone together in the same location. We’ve had tremendous success as a distributed team. But regardless, we wanted to add an edge to our collaboration and creativity, and connect in-person. Our journey, the results that came of it, and the economics behind it are all explained thoroughly in the post that follows.

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