How to Hire/Interview a Mobile App Developer and What to Look For?

Job interviews are uniquely stressful events. What many don’t appreciate is how much interview stress goes both ways. The interviewer tasked with hiring the best candidate is under almost, but not quite, as much stress as the interviewee facing the questions as there’s a lot at stake and many small details to tease out in just an hour’s worth of conversation.

A good interview is just barely enough time to get a professional first impression. Yet, from that impression, you’re expected to find out if they have the credentials, experience, and aptitude for the role while assessing if they’re a good fit for the office culture.

With so much to cram into just one or two short meetings, it’s important to get things right. Having the right plan, technique, and asking the right questions will go a long way to making that time go just a little bit further. And remember, if you need help selecting the right company, tell us what you need. We can do the work for you and connect you with up to 5 companies within 72h that match your need- all for free.

Get to Know the Candidate

Before you get to the tough questions and technical exams, it’s good to sit down to talk to the candidate face-to-face about the work they’re doing now or what they’ve done in the past. Despite being comparatively informal, this conversation is the one that often generates the most insight into a candidate’s professional experience and knowledge.

Ask to see their portfolio and talk about apps they have worked on or delivered for clients in the past. Experienced app developers invariably have a portfolio to show. They are usually keen to talk about their past apps and successes too.

Ask for details about technologies used and problems encountered when creating specific mobile applications. These provide a great jumping-off point to talk about the features and technologies you want to create in your apps. It’s a great way for the candidate to warm up to the interview by talking about something they know in-depth. If you think you might need help with the conversation, let us help with our article on the future of mobile app engineering.

Start With the Basics

Starting with some simple, on-topic technical questions is an ideal way to get an interview off on the right foot. General topics such as popular platforms, useful apps, and their favourite developer tools can serve as a helpful introduction to more technical subjects further down the line.

Starting with the general before moving to the specific serves two main purposes:

• It starts the interview with some friendlier questions to get candidates interested and enthusiastic about the topic
• It effectively filters out candidates without the experience of the specific technologies and languages employed

Some good starting points may be to look over some features or code that your developers have worked on previously. Identifying new features or fixing simple bugs can be a great way for candidates to show off their practical experience in a real-world setting.

Alternatively, more general questions about apps and programming can help to provide a technical warm-up to more in-depth conversations. To get started you might want to be up to date on the latest mobile app frameworks.

Some interview questions to start you off:

• Describe the various states of an app and when transitions between these states occur (app lifecycle)
• Describe the benefits of inheritance in Object-Oriented Programming
• Tell me what languages you’ve found useful for app development

Get To Know a Candidate’s Coding Knowledge

One of the critical skills you need a candidate to have is knowledge of the languages you’re employing them to write. Some short, relatively simple questions to this effect will seem almost trivial to the right candidate. Yet, every hiring manager in the world has stories of candidates applying for positions without knowing the language specified. It pays to be safe rather than sorry.

A five-minute test, near the top of the interview, can save a great deal of time further down the road. There's no substitute for simply looking at code. Theoretical questions just don’t test the same skill-set. Code examples used later in the interview should be more complex than those used to test the basics.

Removing comments and asking a candidate to describe its functionality is a great way to determine how much they know and what they can quickly pick up. The payoff is that a candidate who can show an understanding of production code at an interview will have no problem settling into the team and getting up to speed.

Alternative options would be to implement a simple program in the language specified. This can be a short question on pen and paper, to sort a simple list or complete a function specific to the firm’s area of interest. The goal of the exercise should be to demonstrate an understanding of the language and its features rather than write picture-perfect code.

Ways to test a candidate’s coding skills

• The best code examples come from your existing codebase as these are the problems the candidate is being hired to solve
• A before and after snapshot of a bugfix within a method provides an excellent interview question with a ready-made answer with which to compare a candidate’s response
• You may ask the candidate to talk through or document their solution to give you a deeper understanding of their professional communication skills

Practical Knowledge

A mobile app developer with some experience under their belt will bring a lot more value to the team than just coding know-how. Experience with various architectures, alternate ways to implement features, and different deployment methods are all invaluable when it comes to outlining the right strategy to move products forward.

It’s important to get an idea of each candidate’s experience in fields such as testing and continuous integration (CI). These are fundamental parts of professional app development that an experienced candidate should know.

Here you can build on work already done at an earlier round of questions. Asking a candidate to outline or write tests for code described earlier provides them with an opportunity to demonstrate a deeper understanding and gives you the chance to dig deeper too.

How to test their practical skills?

• Ask the candidate to write tests for the methods and code provided or written
• Ask how testing could be improved given more time and what these improvements might look like

Big Picture Knowledge

Almost as important as being able to write code is being able to deploy, test, and publish it. Candidates with mobile app development experience should know each of these processes back to front.

Ask a candidate to talk through this process from beginning to end to get to know their understanding of the application development lifecycle. Compare their answers to the company’s existing processes and assess how the candidate will fit into them. It may be that the company can learn as much from the candidate as the other way round.

Ask for a rough timetable of each stage of the application development process. It can be helpful to understand their estimates and the type of application development they have done before. Candidates from smaller teams tend to skew towards shorter timescales with less room for slip. Candidates more accustomed to process and verification lean towards longer stages, increased time for testing and refinement, and more room for changes.

How to find out whether they have an eye on the bigger picture?

• It can be helpful to ask candidates to provide time estimates for application development in a number of sprints. This provides an insight into their knowledge and experience of agile development methodologies
• Asking the candidate to add features, reduce time-to-market, or how to use additional available time can help you understand what they see as the most important parts of the process

Hiring A Mobile App Developer

In most areas, very little of the interview is about the specific answers to the questions asked. It’s more important how the questions are answered.

Pay close attention to how candidates solve problems and, more importantly, how they communicate those problems and solutions to the rest of the team. How a candidate communicates in an interview should provide an insight into how they will communicate in a development team.

While no interview process will ever be 100% perfect, asking the right questions can provide the window you need to find the right candidate for the role. If you need help selecting the right company, tell us what you need. We can do the work for you and connect you with up to 5 companies within 72h that match your need- all for free.

Five essential app developer interview questions

Tell me about some of the mobile apps you have developed

An excellent way to get a candidate talking about mobile apps is to talk about some of their best previous work. This helps to identify their existing skill-set and allows them to discuss how they have learned new technologies in the past. Being able to point to successful apps in the marketplace or app store at the current time is a significant bonus.

Tell me about the most difficult challenge you’ve faced as a mobile app developer

Here you’re interested in finding out the depth of their experience as much as their ability to solve problems. A candidate who has faced their largest challenges in IDEs and tooling is likely to have comparatively little experience of complex development challenges.

What is the difference between native mobile app design, cross-platform applications, and responsive web design?

Candidates should understand the implications for performance, UI, and functionality when using web apps over native or cross-platform applications. They should be able to contrast this with the rapid time-to-market of a hybrid app and cost-benefit advantages.

What are some specific advantages and disadvantages of both Android and iOS?

Candidates should be able to state some pros and cons of each system outside of mere preference. The comparatively open platform, flexible design, and wider reach of Android are likely favourites, as are the UI priorities, security, and privacy offered by iOS.

What information do you need before you start coding an app?

Candidates should demonstrate an understanding of the complete lifecycle of app development rather than just the immediate requirements. Some suitable answers would include details about deployment, target audience, existing products, design documents, and application assets.