Hiring guide for Elixir Phoenix Engineers

Elixir Phoenix Developer Hiring Guide

Elixir Phoenix is a highly efficient programming language built on the Erlang virtual machine (BEAM), designed for building scalable and maintainable applications. It was developed by José Valim, a former member of the Ruby on Rails core team, who sought to create a language that combined Ruby's expressiveness with Erlang's robustness. Introduced in 2011, Elixir Phoenix has gained popularity for its real-time system capabilities and fault-tolerance. Its Phoenix framework is particularly noted for handling concurrent connections, making it ideal for web development. The language continues to evolve under the stewardship of Plataformatec, Valim's software consultancy company.

Ask the right questions secure the right Elixir Phoenix talent among an increasingly shrinking pool of talent.

First 20 minutes

General Elixir Phoenix app knowledge and experience

The first 20 minutes of the interview should seek to understand the candidate's general background in Elixir Phoenix application development, including their experience with various programming languages, databases, and their approach to designing scalable and maintainable systems.

How would you install Elixir?
You can install Elixir using a package manager like Homebrew on macOS, Chocolatey on Windows, or apt-get on Ubuntu. Alternatively, you can download precompiled packages from the Elixir website.
What are the basic data types in Elixir?
The basic data types in Elixir are integers, floats, booleans, atoms, strings, lists, and tuples.
How would you define a function in Elixir?
Functions in Elixir are defined with the 'def' keyword inside a module. For example, 'defmodule MyModule do def my_function do end end'.
What is pattern matching in Elixir?
Pattern matching in Elixir is a way to match complex data types, destructure them, and access their contents. It's a fundamental part of the language and is used extensively.
How would you handle errors in Elixir?
Elixir uses a mechanism called 'let it crash' for error handling. Instead of trying to handle every possible error, processes are allowed to crash and supervisors restart them when necessary.
The hiring guide has been successfully sent to your email address.
Oops! Something went wrong while submitting the form.

What you’re looking for early on

Does the candidate demonstrate a solid understanding of Elixir and Phoenix?
How proficient is the candidate in concurrent programming?
Can the candidate effectively communicate their thought process and problem-solving approach?
Has the candidate worked on any projects or tasks that utilized Elixir Phoenix?

Next 20 minutes

Specific Elixir Phoenix development questions

The next 20 minutes of the interview should focus on the candidate's expertise with specific backend frameworks, their understanding of RESTful APIs, and their experience in handling data storage and retrieval efficiently.

What is the difference between a list and a tuple in Elixir?
Lists and tuples are both collection types in Elixir. The main difference is that accessing the length of a list is an O(n) operation, while for tuples it's an O(1) operation. Also, updating or adding elements to a list is efficient, while for tuples a new tuple must be created.
How would you create a GenServer in Elixir?
A GenServer in Elixir can be created by using the GenServer behaviour module. You would define a module, use GenServer, and implement the necessary callback functions like handle_call, handle_cast, and init.
What is the role of the Supervisor in Elixir?
A Supervisor in Elixir is a process which supervises other processes, called workers. It is responsible for starting, stopping, and managing these worker processes. If a worker process terminates abnormally, the supervisor can restart it.
Describe the difference between 'handle_call' and 'handle_cast' in a GenServer.
'handle_call' is a synchronous function that blocks the caller until it gets a response, while 'handle_cast' is an asynchronous function that sends a message and immediately returns a 'noreply' response.
How would you test a Phoenix application?
Phoenix applications can be tested using the built-in ExUnit testing framework. You can write unit tests for your models and controllers, and integration tests for your routes and views.
The hiring guide has been successfully sent to your email address.
Oops! Something went wrong while submitting the form.

The ideal back-end app developer

What you’re looking to see on the Elixir Phoenix engineer at this point.

At this point, a skilled Elixir Phoenix engineer should demonstrate strong problem-solving abilities, proficiency in Elixir Phoenix programming language, and knowledge of software development methodologies. Red flags include lack of hands-on experience, inability to articulate complex concepts, or unfamiliarity with standard coding practices.

Digging deeper

Code questions

These will help you see the candidate's real-world development capabilities with Elixir Phoenix.

What does this simple Elixir code do?
IO.puts("Hello, World!")
This code prints the string 'Hello, World!' to the console.
What is the output of this Elixir code?
This code will print the range '1..5' to the console.
What does this Elixir code do?
list = [1, 2, 3, 4, 5]
Enum.map(list, fn x -> x * 2 end)
This code multiplies each element in the list by 2 and returns a new list with the results.
What does this Elixir code do?
Task.async(fn -> 1 + 2 end)
|> Task.await()
This code runs the function '1 + 2' asynchronously in a separate process and waits for the result.

Wrap-up questions

Final candidate for Elixir Phoenix Developer role questions

The final few questions should evaluate the candidate's teamwork, communication, and problem-solving skills. Additionally, assess their knowledge of microservices architecture, serverless computing, and how they handle Elixir Phoenix application deployments. Inquire about their experience in handling system failures and their approach to debugging and troubleshooting.

What is Plug in Phoenix?
Plug is a specification for composable modules in web applications. It provides a unified interface for web server adapters, web frameworks, and middleware. Phoenix uses Plug to handle routing and requests.
How would you handle real-time communication in a Phoenix application?
Phoenix provides a feature called Channels for real-time communication. Channels use WebSockets to provide bi-directional communication between the server and the client.
What are Ecto Schemas in Phoenix?
Ecto Schemas are used to map any data source into an Elixir struct. They provide a way to define both the fields and their type, and the relationships between different schemas.

Elixir Phoenix application related

Product Perfect's Elixir Phoenix development capabilities

Beyond hiring for your Elixir Phoenix engineering team, you may be in the market for additional help. Product Perfect provides seasoned expertise in Elixir Phoenix projects, and can engage in multiple capacities.