Mastering the Technical Phone Screen for Apps Developers

Welcome to the Interview Loop series where we go over each step of your interview loop.

Remember, while some job interviews may include all these sessions, others might involve a subset. Prepare accordingly.

Some companies have 2 initial phone screen- a general one and a technical one. Other combine the two. Make sure to review the Initial Phone Screen guide. Much of it applies to the Technical Phone Screen.

When confronted with a Technical Phone Screen, it’s not always clear what your technical interviewer might ask you.

Sometimes, it will be competency specific- that’s often the case for smaller startups. Bigger companies (think FAANG and such) might assess more general software engineering competencies.

Let’s break it down.

Before taking the interview

As always, start with preparation.

Don’t get into the technical phone screen blind, that’s the best way to fail.

Instead, ask your Hiring Manager or recruiter what to expect for the technical phone screen. If you don’t get any info, you can also search on Glassdoor to see if any other interviewee dropped some clues.

If you know what to expect, you can prepare accordingly.

Startup Technical Phone Screen

Startups tend to probe for the skills and experience they’re hiring for over general engineering skills.

For an Apps Developer, it means that you need to know your field quite well. Extra points if you have industry experience, whether it’s from past employment or personal projects.

Sometimes, you’ll be asked how you would build a given app, what technologies you would use, and how you would architect it.

Before the interview, spend some time researching how you would build their apps yourself if the project started from scratch today and you were the sole developer for it. The closer you get to the same answers they got to, the more chances you have to nail the interview.

Be on top of recent industry trends

One trap apps developers often fall into is to not stay up to date with current apps development practices. Say you’ve worked at the same company for the past 3 years, it’s possible that you’ve been working on a legacy codebase. This means you might have not worked with more recent tools that are now available to make your job easier.

So stay on top of the technologies you work with and use the new tools available to you. If not at your current job, implement them in personal projects.

Know your apps architecture

One of the most important trait of Apps Experts is that they know how to build scalable apps architecture.

There’s a lot of online resources for this, but be on top of your game.

Those who describe app architecture from 8 years ago are almost always ruled out at this stage.

Brush up CLEAN architecture, how to design streams, a robust data layer, dependency injection and composable UI.

Decompile their app

This might be controversial but the best way to know how they built their existing app (if they have one) is to decompile it.

Get a list of libraries and protocols they’re using, and spend some time getting familiar with it.

If you can talk confidently about the technologies they’re using, the startup you’re interviewing with will look at you as someone who can ramp up quickly on their project and you’ll be much more likely to get to the next step of the interview.

Large Company Technical Phone Screen

Large companies tend to run technical interviews for Apps Developers a little differently. While startups are often focused on short to mid term goals, large companies tend to expand their horizons a bit. When hiring, they don’t only probe to know if an engineer knows the required skills. They also try to understand if you’re a well rounded software engineers and a problem solvers so you can be deployed on different types of projects if needed. Sometimes, your apps expertise doesn’t come as valuable because they built their own frameworks on top of the technologies you work with so basic apps experience becomes less relevant.

While you should be ready for the type of technical screens startups do, I also recommend brushing up on algorithms and system designs.

And as always, go on Glassdoor to see if there’s any pointers on what direction the technical phone screen may go for the company you’re interviewing with. Large companies tend to be better documented than startups on Glassdoor so maximize your chances of success by studying what questions you may get.

Algorithms

I’m not a big fan of algorithm interviews. Often time, they’re pretty irrelevant to what people end up doing on the job. However, they can be an effective way for interviewers to know how you work through technical challenges and problem solve.

Algorithm questions during the phone screen are usually simpler than a dedicated algorithm interview. You might be asked to live code and work through a given problem with an interviewer.

For FAANG type companies, the best resource to prepare for algorithm problems is Cracking the Coding Interview . It provides over 180 coding exercises you can prepare at home.

There’s no shortcut to prepare for algorithm interviews. The trick is to do a lot of them, and you may need several weeks to prepare for it. So get a head start and crank through some coding exercises weeks before you start your search if you can.

System Designs

Another common line of questioning for large companies are System Designs. This is a more abstract interview where you will be asked about a clear breakdown of how a given system works. You’re expected to either know your field well (say how you would architect a given mobile app), or how broader systems work (covering frontend, backend and beyond).

There’s little common themes across these interviews so once again, doing your research ahead of time should point you in the right direction for a given company.

Here are some commonly found System Designs questions you may be asked during a System Designs Technical phone Screen:

How would you build an offline synchronization system?
How would you build a full fledged token based authentication system?
How would you build a push notification system from scratch?
How would you build an online battlefield game?

Conclusion

Technical phone screens vary a lot and once again, preparation is the name of the game.

For small companies, know your tech and industry.

For bigger ones, find the questions you’ll be asked and prepare for it. Some of the content in our subsequent guides around algorithms and system designs may be useful for the phone screen too.

You’re expected to be on top of your game to talk technical, but every other trait mentioned in the Initial Phone Screen guide is relevant too (Communications, Professionalism, Enthusiasm etc…).

Nail this interview and you have your first foot in the door with the company you’re aspiring to.

Mastering the Technical Phone Screen for Apps Developers

Before taking the interview