Top Scala Interview Questions: Hire the Right Scala Engineer

Finding the right Scala developer for your remote team can be tricky. You want to snag somebody who really knows Scala, jives with your company culture and has those key remote soft skills to make your team click. 

As you go to hire a Scala engineer, you’ll want to cover all the bases with your Scala candidates. By going through our personal, theoretical and practical questions, you can make sure your candidate has the Scala skills, as well as the soft skills to earn a spot at your company. 

Let’s break down the top Scala interview questions, so that you feel prepared to get your dream Scala developer once and for all. 

1. Personal Scala Interview Questions

To start off your remote Scala interview, go for the personal. This will give the candidate a chance to warm up and show his/her personality. You’ll also get a sense of how the candidate communicates naturally with you. 

Not sure what to ask your Scala engineer candidate? Use some of our spark Scala interview questions below:

  • Tell me about a technical challenge you faced and how you resolved it.
  • Tell me about your preferred development environment. 
  • What’s a cool project you’ve worked on recently?
  • What testing framework do you use? For which languages?
  • Have you ever disagreed with your manager’s decision? When?
  • How do you handle stress or high pressure?
  • Tell me about a time when you made a mistake.
  • What do you like to do outside of work?

Now that you’ve learned a little more about the candidate, it’s time to test his/her Scala skills. After all, you want cream-of-the-crop Scala developers! 

2. Theoretical Scala Interview Questions

Our theoretical Scala interview questions will help get a pulse on your candidate’s Scala abilities. It’s important to note that a candidate doesn’t have to answer all these questions correctly. Oftentimes Scala engineers have strengths in certain areas and weaknesses in other areas. 

In general, these Scala coding interview questions will let you see how the candidate thinks. Check that the candidate has the knowledge level you’re looking for, plus the confidence to field questions he/she isn’t sure about. When a candidate communicates well, despite not knowing the full answer, this is a good clue that he/she will work effectively with clients. 

Here are some top theoretical Scala interview questions to ask:

General:

  • What are the advantages of using Scala?
  • Is Scala compatible with Java?
  • How does Scala compare to other JVM languages?
  • How do you compile and run a Scala program?
  • What is Scala’s Backward Compatibility Issue?
  • Does Scala support Operator Overloading?
  • What are the advantages of companion objects?
  • What are the different Scala identifiers?
  • What are the different Scala Literals?
  • How do you format a string in Scala?
  • What is exception propagation in Scala?
  • How is Scala both a Functional and an Object-Oriented language?
  • Why do we need App in Scala?
  • How can I append a List in Scala?

Please explain:

  • Null.
  • Unit.
  • REPL.
  • If..else.
  • Scala Map.
  • Closure.
  • Option.
  • Scala Trait.
  • Tupules.
  • Packages.
  • Monad.
  • Akka.
  • ofDim.
  • BitSet.
  • Vector.
  • Streams.
  • Vararg.
  • Tail-recursion.
  • Higher-order function.
  • Auxiliary constructor.
  • Type interference.
  • Yield.

What’s the difference between…?:

  • Scala Int vs. Java’s java.lang.integer.
  • Val vs. var vs. def.
  • Object vs. class.
  • Array vs. list.
  • Unapply vs. apply. 
  • Call-by-value vs. call-by-name.
  • Null vs. Nil vs. None vs. Nothing.
  • Case class vs. regular class
  • Function vs. Method.
  • Concurrency vs. Parallelism.
  • OOP vs. FP style loops.

Of course, you don’t have to ask all these interview questions on Scala. Select ten or so questions to test your candidate and get a better idea of how he/she thinks and communicates. Be sure to ask about areas that your team needs more expertise in. Ideally, you can fill any knowledge gaps with this new team member.

3. Practical Scala Interview Questions

Now that you know your candidate’s theoretical knowledge, it’s time to see his/her know-how in practice. Remember that to do these practical Scala interview questions, your candidate will need time and space to complete them. For remote interviews, ask candidates to show work on a blank Google doc and then share his/her screen. Or, provide a whiteboard app so that you can see the candidate’s work in real-time. 

If you prefer, you can also set up an online practical test for him/her to complete. If you’re short on time, this is a good solution. Otherwise, watching how the candidate solves a problem can give you insight into how the candidate works under pressure, as well as his/her coding style. 

Some of the best practical Scala interview questions to ask include:

  • Prove that Scala is a language statically/strongly typed.
  • Generate an Infinite loop.
  • Explain Pattern Matching in Scala with an example.
  • What is the result of x+y*z and why?

You can also add practical questions by taking any theoretical questions and asking the Scala developer to prove or give an example of that case.

Final Tips for Remote Scala Interviews

These Scala interview questions can be used for in-person or remote interviews. However, if your interviews are remote, you should keep our tips in mind so that you don’t get tripped up remotely. Making the most of your remote interviews is easier than you think. Just follow these guidelines for successful remote Scala interviews:

  • Check your tech: Make sure your connection and video call app are working well. There’s nothing more unprofessional than a call that cuts in and out. The remote interview is also a test of your day-to-day communications.
  • Look up the candidate’s digital footprint: Before you jump on the call, look over the Scala engineer's profile and do a quick Google search. You may find an interesting project to ask about or an article on LinkedIn that you want to know more about. Your interview will be more rewarding if you take the time to know the candidate beforehand. 
  • Record the interview: Most video call apps these days let you record interviews. This is helpful if you’re interviewing lots of candidates on the same day and want to look over the details later. Or, you can try voice-to-text apps like Otter to keep tabs on each candidate. 
  • Test the candidate’s remote-friendly qualities: One of the biggest interview mistakes is only looking at hard skills and forgetting soft skills. Check that your candidate has remote-friendly qualities that would make him/her work successfully at your company. Be on the lookout for great communication skills, tech know-how, a proactive mindset, and outside interests. Having a well-rounded candidate can make a huge difference for your team. 

Hiring the ideal Scala developer for your remote team may be hard, but these interview questions and tips will move you in the right direction. Use our personal, theoretical and practical questions to get a clear understanding of the candidate’s strengths and weaknesses. 

If you’re having trouble finding great Scala engineers, you might also consider trying out specialized platforms for developers. These platforms can help connect you to top talent, so you can hire new staff members or fill your staff augmentation needs. They can also help if you’re looking for candidates with other expertise, for example hiring Node.JS developers. Whatever you’re looking for, these platforms are a go-to spot for boosting your candidate search. 

Go on, we dare you to find the right Scala engineer for your company!

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We’ve had great results with TECLA’s recruiting. The developers we hired allowed us to drastically increase the pace of our development process and try new things more efficiently. This is crucial for us as we continue to grow!

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