Engage Elite Elixir Developers

{{interview-qa-header="/hiring-docs/elixir"}}

1. What experience do you have with Elixir's Phoenix framework?

I have worked with the Phoenix framework for the past three years. During this time, I have built several web applications using Phoenix, including an e-commerce platform and a social networking site. I am comfortable with the framework's MVC architecture, channels, and LiveView functionality.

2. Can you describe your experience with Elixir's OTP (Open Telecom Platform)?

I strongly understand OTP and its various components, such as supervisors, gen_servers, and applications. I have used OTP to build highly fault-tolerant systems, including a distributed messaging platform that handles over a million daily messages.

3. What is your experience with testing in Elixir?

I have extensive experience with testing in Elixir, including unit testing, integration testing, and end-to-end testing. I use ExUnit for unit testing and Wallaby for browser testing. I also have experience with property-based testing using the PropEr library.

4. Have you worked with other functional programming languages besides Elixir?

Yes, I have worked with Haskell and Erlang in the past. I find that the functional programming paradigm fits well with my problem-solving approach and leads to more maintainable code.

5. Can you give an example of how you've used Elixir's concurrency features in a project?

In a recent project, I used Elixir's GenStage to implement a pipeline for processing real-time data from a streaming source. The pipeline could handle large volumes of data with low latency, thanks to Elixir's efficient concurrency model.

6. What is your experience with databases in Elixir?

I have worked with several databases in Elixir, including PostgreSQL, MySQL, and MongoDB. I am very familiar with Ecto, Elixir's database wrapper, and have used it to build complex queries and migrations.

7. Can you describe a challenging bug you had to fix in an Elixir project?

In one project, we had a concurrency issue that caused intermittent failures in the application. After some investigation, we found that the issue was related to race conditions in our GenServer processes. We resolved the issue by implementing a more robust locking mechanism.

8. Have you contributed to any open-source Elixir projects?

Yes, I have contributed to several Elixir projects, including the Ecto library and the Phoenix framework. I enjoy giving back to the Elixir community and learning from other developers' contributions.

9. Can you give an example of how you've optimized performance in an Elixir application?

In a recent project, we had a performance bottleneck related to the amount of data we were processing in memory. To address this, we used Elixir's Streams API to process the data and reduce memory usage lazily. We also implemented a caching layer to reduce the number of database queries.

10. How do you stay updated with new developments in the Elixir ecosystem?

I stay updated with the Elixir ecosystem by reading the Elixir forum, following Elixir experts on Twitter, and attending conferences and meetups. I also enjoy experimenting with new libraries and tools in my personal projects.

{{tech-qa-header="/hiring-docs/elixir"}}

1. Write a function that takes a list of integers and returns the sum of all even numbers in the list.

_Answer:

defmodule Math do
  def sum_of_evens(numbers) do
    Enum.filter(numbers, fn n -> rem(n, 2) == 0 end)
    |> Enum.sum()
  end
end

Math.sum_of_evens([1, 2, 3, 4, 5, 6]) #=> 12

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2. Implement a recursive function that calculates the nth Fibonacci number.

_Answer:

defmodule Fibonacci do
  def fib(0), do: 0
  def fib(1), do: 1
  def fib(n), do: fib(n - 1) + fib(n - 2)
end

Fibonacci.fib(6) #=> 8

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3. Write a function that takes a string and returns the count of each unique character in the string.

_Answer:

defmodule CharCount do
  def count_chars(string) do
    string
    |> String.graphemes()
    |> Enum.reduce(%{}, fn char, acc ->
      Map.update(acc, char, 1, &(&1 + 1))
    end)
  end
end

CharCount.count_chars("hello") #=> %{"e" => 1, "h" => 1, "l" => 2, "o" => 1}

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4. Implement a module that uses GenServer to maintain a counter that can be incremented and decremented.

_Answer:

defmodule Counter do
  use GenServer

  def start_link(opts \\ []) do
    GenServer.start_link(__MODULE__, [], opts)
  end

  def init(state) do
    {:ok, 0}
  end

  def increment(pid) do
    GenServer.cast(pid, :increment)
  end

  def decrement(pid) do
    GenServer.cast(pid, :decrement)
  end

  def handle_cast(:increment, count) do
    {:noreply, count + 1}
  end

  def handle_cast(:decrement, count) do
    {:noreply, count - 1}
  end

  def get_count(pid) do
    GenServer.call(pid, :get_count)
  end

  def handle_call(:get_count, _from, count) do
    {:reply, count, count}
  end
end

{:ok, pid} = Counter.start_link()
Counter.increment(pid)
Counter.increment(pid)
Counter.decrement(pid)
Counter.get_count(pid) #=> 1

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5. Write a function that takes a list of maps and returns a new map with the keys of the maps as keys in the new map, and the values of the maps as values in the new map. If there are duplicate keys, the last value should be used.

_Answer:

defmodule MapUtils do
  def merge_maps(maps) do
    Enum.reduce(maps, %{}, fn map, acc ->
      Map.merge(acc, map)
    end)
  end
end

MapUtils.merge_maps([%{a: 1, b: 2}, %{c: 3, b: 4}]) #=> %{a: 1, b: 4, c: 3}

{{job-qa-header="/hiring-docs/elixir"}}

Introduction

Creating an excellent Elixir developer job posting is essential to attracting top talent and finding the best candidates for your organization. Knowing what to ask when hiring for an Elixir development role can be challenging, but it doesn't have to be. Here's a job posting template, developer interview questions, and an explanation of each section.

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Job Title

The job title should be clear and concise and accurately reflect the role's responsibilities. A title like "Elixir Developer" is appropriate.

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Elixer Developer Job Description

The job summary should provide a brief overview of the role's responsibilities and requirements. It should include a concise description of the company and its culture to help potential candidates determine whether they would be a good fit for the position. This section should be written in clear and straightforward language.

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<span class="guide_indent-text">Example:</span>

<p span class="guide_indent-text">We are seeking an experienced Elixir Developer to join our growing team. In this role, you will be responsible for developing and maintaining Elixir-based applications, collaborating with cross-functional teams, and ensuring the quality of our software products. Our company is committed to creating a culture of collaboration, innovation, and growth, and we are looking for candidates who share these values.</p>

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Responsibilities

The responsibilities section should outline the primary duties and tasks that the Elixir developer will be responsible for. Be specific and detailed in this section to give candidates a clear understanding of what Elixir development services will be required of them. It's also helpful to include the level of experience required for each responsibility.

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<span class="guide_indent-text">Example:</span>

<ul><li>Develop and maintain Elixir-based applications</li><li>Collaborate with cross-functional teams to design, develop, and deploy software products</li><li>Ensure the quality of software products through testing and debugging</li><li>Continuously improve software development processes and tools</li><li>Stay up-to-date with emerging trends and technologies in Elixir development</li></ul>

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Elixir Developer Requirements

The requirements section should list the necessary qualifications, experience, and education required for the role. This section should include both the minimum requirements and the preferred qualifications. It's important to be clear and specific about what is required for the role to avoid receiving applications from unqualified candidates.

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<span class="guide_indent-text">Example:</span>

<ul><li>Bachelor's degree in Computer Science, Engineering or related field</li><li>3+ years of experience in Elixir development</li><li>Strong understanding of Elixir, OTP, and Phoenix frameworks</li><li>Experience with agile software development methodologies</li><li>Excellent problem-solving skills and attention to detail</li></ul>

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Preferred Qualifications

The preferred qualifications section should list any additional qualifications, experience, or education that would be beneficial but are not strictly required. This section is an excellent opportunity to attract top talent by highlighting unique qualifications or qualities that set your organization apart. Adding specific qualifications about your project is a great way to get everyone on the same page when hiring an Elixir developer.

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<span class="guide_indent-text">Example:</span>

<ul><li>Experience with distributed systems and microservices architecture</li><li>Knowledge of containerization technologies like Docker and Kubernetes</li><li>Strong understanding of functional programming concepts</li><li>Experience with front-end development technologies like React or Angular</li></ul>

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Salary and Benefits

The salary and benefits section should be straightforward and clear. You should include the salary range for the position and any additional benefits, such as health insurance, retirement plans, and paid time off. Be sure to include your organization's unique benefits, such as flexible work hours or tuition reimbursement.

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<span class="guide_indent-text">Example:</span>

<ul><li>Competitive salary based on experience and qualifications</li><li>Health, dental, and vision insurance</li><li>401(k) retirement plan with employer match</li><li>Flexible vacation and PTO policy</li><li>Opportunities for professional development and growth</li></ul>

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How to Apply

This section should outline the process for applying for the Elixir developer position. Include specific instructions or requirements, such as a cover letter, resume, or code samples.

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<span class="guide_indent-text">Example:</span>

<p span class="guide_indent-text">To apply, please submit your resume and cover letter to [insert contact email or application link here]. In your cover letter, please briefly summarize your experience with Elixir and your reasons for applying to this position. We look forward to hearing from you!</p>

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Conclusion

By following this template for an Elixir developer job posting, you can attract the best candidates and ensure that you find the right person for the job. Remember to be specific about the requirements and responsibilities, highlight the benefits, and provide clear instructions for how to apply. Good luck in your search for a talented Elixir developer!

{{challenge-qa-header="/hiring-docs/elixir"}}

Challenge Instructions:

Implement a Queue data structure in Elixir with the following methods:

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• enqueue(element): Add an element to the end of the queue.
• dequeue(): Remove and return the element at the front of the queue.
• front(): Return the element at the front of the queue without removing it.
• isEmpty(): Return a boolean indicating whether the queue is empty or not.

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Your implementation should be based on a singly linked list and should include the following requirements:

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• All methods should have O(1) time complexity.
• You should implement the Queue data structure using a module and processes.
• You should include appropriate tests to ensure the correctness of your implementation.

_Answer:

defmodule Queue do
  defstruct front: nil, back: nil

  def new, do: %Queue{}

  def enqueue(queue, element) do
    case queue.back do
      nil ->
        %Queue{front: element, back: element}

      _ ->
        queue =
          queue
          |> Map.put(:back, element)
          |> Map.update(:front, &(&1))
        queue
    end
  end

  def dequeue(queue) do
    case queue.front do
      nil ->
        {:error, "Queue is empty"}

      _ ->
        front = queue.front
        queue =
          queue
          |> Map.put(:front, front.next)
        {front.value, queue}
    end
  end

  def front(queue) do
    case queue.front do
      nil ->
        {:error, "Queue is empty"}

      _ ->
        queue.front.value
    end
  end

  def isEmpty(queue) do
    queue.front == nil
  end
end

defmodule QueueTest do
  use ExUnit.Case

  test "enqueue/dequeue" do
    queue = Queue.new
    queue = Queue.enqueue(queue, 1)
    queue = Queue.enqueue(queue, 2)
    queue = Queue.enqueue(queue, 3)

    assert Queue.front(queue) == 1
    assert Queue.dequeue(queue) == {1, %Queue{front: 2, back: 3}}
    assert Queue.dequeue(queue) == {2, %Queue{front: 3, back: 3}}
    assert Queue.dequeue(queue) == {3, %Queue{front: nil, back: nil}}
    assert Queue.dequeue(queue) == {:error, "Queue is empty"}
  end

  test "isEmpty" do
    queue = Queue.new
    assert Queue.isEmpty(queue) == true

    queue = Queue.enqueue(queue, 1)
    assert Queue.isEmpty(queue) == false
  end
end

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In conclusion, we hope this Elixir Developer Hiring Guide has been a valuable resource in your search for top Elixir talent. By utilizing the conversational and technical interview questions, job posting template, and coding challenge provided in this guide, companies can confidently evaluate candidates and hire the best Elixir developers for their needs. With the right team in place, companies can leverage Elixir's power to build highly scalable and reliable web applications that meet the demands of today's fast-paced digital landscape.