How I Hire at Mozilla

As a manager, one of my most important responsibilities is hiring. While I’m hiring, I spend a lot of time sifting through resumés, screening candidates, and eventually doing interviews. This is both fun and depressing at the same time, because you get to meet and learn a lot about some interesting people, but you also have to wade through a lot of terrible resumés and phone screens. I want to share some things that I look for during the hiring process, and some tips for potential job-seekers about how to deal with recruiting:

Read the Job Description

Please read the job description before applying for a job! I put a lot of effort into writing a job description, and I try very hard to describe both the job responsibilities and the necessary and desirable skills. Your cover letter should show some evidence that you’ve thought about applying for this particular job.

Write a Good Cover Letter

Periodically, I see articles advising job-seekers to ditch the cover letter. This is terrible advice. I read cover letters carefully. In fact, the cover letter sometimes gives me a better sense for your skill level and ability to do the job than your resumé.

Grammar and Spelling Matter

Every job I’ve ever posted has required good communication skills, and your cover letter is the first evidence of your communication skills. It doesn’t need to be more than a paragraph or two; I’d love to know why you think that this job is a good fit, and some evidence that you read the job description. Spelling and grammar are important.

I’m Picky

The last time I posted a job position, I screened more than 800 resumés, did almost 100 phone screens, and did five interviews before I found the right person. It took six months. It’s better for Mozilla if I’m too picky and reject a qualified candidate than if I’m not picky enough and accept a bad candidate. Please don’t take rejection as a comment on your personal worth. I’m going to reject many people during this process.

Smart and Gets Things Done

Joel Spolsky is right: I’m primarily looking for somebody who is smart and gets things done. When I’m scanning through resumés, I’m looking for evidence that you’ve gotten things done in the past. If you’re just coming out of school, internship and open-source project experience helps. If you’ve been working, I want to see some description of the things you’ve gotten done. Be specific: “Led multiple projects to completion” is meaningless. You can expect phone-screen questions about your prior projects. Be prepared to talk about what worked, what didn’t, and how you solved problems.

No Assholes

It may seem obvious, but assholes need not apply. I will reject a technically-qualified candidate for even a whiff of assholery. I use reference checks to try and guard against assholes.

Passion Isn’t Sufficient

At Mozilla we get a lot of applicants who are passionate, either about the open web in general or about Firefox. Passion is great, perhaps even necessary, but it’s not sufficient.

Interview Questions Are Based on Your Resumé

In phone screens and interview panels, I try very hard to base my questions on the things that you already know. If your resumé says that you are a master of C++, you should expect that there is at least one person on the interview panel who will grill you on C++ in excruciating detail. If you say that you know statistics, you had better be able to answer detailed questions about statistics.

Don’t overstate your skills. If you have written a couple scripts in Python, you are familiar with Python, not proficient. More than once I’ve rejected people because they claimed to be a master of C++ debugging but didn’t know how a vtable is structured in memory. Knowing vtable layout isn’t usually a job prerequisite, but if you are a master of C++ debugging you’d better know how that works in detail.

If you claim to be a master of both Python and JavaScript, expect me to ask you detailed questions about how Python and JS closures and methods work, how they are different in JS and python, how JS this-binding is different from Python bound methods, and other details of the language. I will be impressed if you can discuss these questions intelligently, and reject your application if you can’t.

I Value Code Reading

I value people who can learn new code quickly. You’re going to need to be comfortable learning new systems, libraries, and languages. My team in particular often touches large swaths of the Mozilla codebase; you will be expected to be able to read and understand new code quickly. You can expect an interview session entirely dedicated to reading and explaining a piece of code that you’ve never seen before. Perhaps it will be reviewing a patch, or trying to find a bug in a piece of code. I’ll try to find a problem in a language that you are already comfortable with, so see above about keeping your resumé honest!

Do You Love Your Tools?

Every good programmer has a toolbox. I don’t care whether you use vim or emacs or Visual Studio or Eclipse or XCode, but I do care that you have an editor and use it productively. I also care that you are proficient using a debugger (or two, or three) and hopefully a profiler (or two, or three). If you can’t tell me why you love your editor or your debugger, it’s likely that you won’t be a successful software engineer.

You need to be proficient in a scripting language. I expect you to be able to use at least one scripting language to process text data, read CSV files, write JSON, and that kind of thing. Mozilla has gravitated toward Python for scripting, and you’ll probably be expected to learn Python if you don’t know it already.

Also, can you type? I’m constantly surprised by applicants who are unable to type quickly and accurately. A significant portion of your job is going to be writing code, and not having mastered the act of typing is probably not a good sign.

Phone Screens

When I conduct a phone-screen, it is usually over Skype video. Please make sure that you have a decent headset and that I will be able to hear you. During a phone screen, I try to include at least one coding question which is typically conducted via etherpad. You should be at a computer with access to the web in order to do this successfully.

By the way, did I mention I’m hiring?

Atom Feed for Comments 5 Responses to “How I Hire at Mozilla”

  1. Grant Says:

    I’m not a coder, but I agree 99%.

    On the job description though, I have been to numerous job interviews where the job is completely different to the description purely because HR or the recruitment agent have written it, not the immediate manager.

  2. Burak KALAYCI Says:

    ‘a low-level language such as C/C++’

    Made me realize how old I am. C was a high level language in my day – and nobody would have argued that :)

  3. Answers and Questions » Blog Archive » How I Do Code Reviews at Mozilla Says:

    […] « How I Hire at Mozilla […]

  4. stoddart Says:

    Great advice on how to be prepared for a developer interview. Heads up, your “I’m hiring” link to open jobs is dead. Of course, it’s over a month old so that makes sense. Since this is a good piece it might be nice to point here instead:

  5. Answers and Questions » Blog Archive » Hiring at Mozilla: Beyond Resumés and Interview Panels Says:

    […] If you’re interested, check out my prior post, How I Hire At Mozilla. […]

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