CodeSubmit Interview Series

The 10 Best Elixir Interview Questions in 2023

What are the top Elixir interview questions? Today, you’ll learn what to ask when you’re interviewing Elixir developers the next time around. Want to learn more? Read on!

Interviewing Elixir developers 

Elixir is a functional, general-purpose, concurrent programming language. It runs in the BEAM virtual machine and builds on top of the Erlang programming language. Erlang and Elixir share the same abstractions for building fault-tolerant, distributed applications. 

Originally, Elixir was meant to be used by large-scale sites and apps to handle large data volumes, so it uses features of Ruby, Erland, and Clojure to create a low-latency and high-concurrency language. 

How do you find the best Elixir developers? Here’s what you need to know. 

Beginner Elixir interview questions

What are the top junior Elixir developer interview questions? In this section, we list questions to ask at your next interview. 

1. Explain the benefits of Elixir. 


Elixir as a programming language has several benefits. These include:

  • Concurrency: Elixir supports multithreading while keeping up performance. 

  • High readability: Elixir’s syntax is easy to understand and the language uses simple expressions to execute commands. In other words, Elixir is simple to grasp and Elixir developers don’t typically need a lot of onboarding. 

  • Phoenix framework: The technology supports real-time processing on the server and client side and makes the migration from Rails to Elixir easy. 

  • High fault tolerance: Elixir includes a failure alert system and it supports the independence of application elements. During a system failure, the components will run on an app hosted on a different server. 

  • High scalability potential: Elixir accommodates the needs of complex AI and IoT apps because it builds on Erlang’s syntax. Apps can simultaneously be run on multiple virtual servers. 

2. What are Elixir modules? 


An Elixir module is a piece of Erlang code. It consists of function declarations and attributes with every module declaration terminated by a period (.) symbol. These modules have a well-defined structure with a value and a tag and either pre-defined or user-defined attributes. 

3. Explain what a compiled language is in comparison to an interpreted language.


Elixir is a compiled language, which means that it’s converted into machine code before it’s executed. Interpreted languages are read and executed line by line by an interpreter program. Compiled languages are typically faster and more effective than interpreted languages. 

4. Which are the Elixir operators? 


There are four Elixir operators. These are arithmetic operators, comparison operators, misc operators, and boolean operators. 

Advanced Elixir interview questions

Now you know what to ask a junior Elixir developer. But what about senior Elixir developers? Let’s find out!

5. What are immutable data structures? 


Immutable data structures can’t be changed after they’ve been created. Once you create an immutable data structure, it will always contain the same data. So if data is shared between different code parts or people, the data stays the same. 

6. How does Elixir handle concurrency? 


A single process is an independent actor according to the model Elixir is built on. While the elements can exchange data, they are managed by the virtual machine. Because the memory of each process is fully isolated, elements are fully independent. Communication relies on mailbox and commands and developers need to use loops to ensure the stability of long-running actors. 

7. Explain the best way to build long-running jobs with Elixir. 


The GenServer offers the best way to build long-running jobs with Elixir. GenServer is a processed-based server with which you can define functions that can be called by other processes. You can build long-running jobs because you are able to easily manage the process and make sure it stays up and running. 

8. Explain what types of variables are available in Elixir. 


Elixir includes four variables:

  • Atoms: Atoms, which can be used as identifiers, are immutable.

  • Strings: Strings can be concatenated and are immutable. 

  • Integers: Integers are whole numbers and are used for mathematical operations.

  • Floats: Floats are numbers with decimal points that can be used for mathematical operations. 

9. What is Port Mapper Daemon? 


The server Port Mapper Daemon supports distributed communications and helps map out node names for specific machine addresses. Earmarks should correspond with the number of nodes in a security group. Port Mapper Daemon uses the 4369 port, which should be kept open. 

10. Explain the best ways to use Elixir in production.


A few steps to take when using Elixir in production include:

  • Use Distillery or a similar tool to create releases for Elixir apps. You can package your app with all dependencies and better manage different app environments. 

  • Use Phoenix or a similar tool to build web apps. Phoenix is a high-performance web framework that is built on top of Elixir. It provides several features out of the box and can make development much faster.

  • Use a tool like ExUnit to write tests for Elixir to ensure that the code is working as it should. This step will also ensure that it’s easier to refactor code and add features. 

Over to you!

There you have it. Now you know what the best Elixir interview questions are. 

Of course, your interview is just step one in selecting a new developer for your team. Another important step is your assessment test.

Assessment tests help you identify top candidates based on their actual skills. 

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