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Elixir Native Implemented Functions (NIFs) is a feature of the Elixir programming language, which was first released in 2011 by José Valim. NIFs allow developers to write functions in languages like C or Rust and then call those functions from Elixir code, enabling high-performance computations. This integration facilitates superior control over system resources while maintaining Elixir's core functionality. The use of NIFs requires careful handling due to its potential risks such as crashing the Erlang Virtual Machine if not properly implemented. However, they have proven essential for tasks that demand efficient execution beyond what pure-Erlang can offer.

Ask the right questions secure the right Elixir Native Implemented Functions talent among an increasingly shrinking pool of talent.

First 20 minutes

General Elixir Native Implemented Functions app knowledge and experience

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

What is the purpose of Elixir Native Implemented Functions (NIFs)?

NIFs are used to write functions in languages like C or Rust and then call them from Elixir code. This is useful for performance-critical code or for interfacing with external libraries written in other languages.

How would you handle memory management when writing NIFs?

Erlang provides a set of functions for allocating and deallocating memory that is managed by the Erlang VM. These functions should be used instead of the standard memory management functions provided by languages like C.

What are the risks associated with using NIFs?

NIFs can cause the entire Erlang VM to crash if they contain bugs, because they run in the same memory space as the VM. They can also block the scheduler if they take too long to execute, which can degrade system performance.

Describe the difference between using NIFs and using Ports in Elixir.

NIFs run in the same memory space as the Erlang VM, while Ports run in a separate OS process. This means that NIFs can be faster, but they can also crash the VM if they contain bugs. Ports are safer, but they have more overhead because data must be serialized and sent between processes.

How would you debug a NIF that is causing the Erlang VM to crash?

You can use standard debugging tools for the language in which the NIF is written, like gdb for C. You can also use the DEBUG macro provided by the Erlang NIF API to print debug information.

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What you’re looking for early on

Does the candidate have a solid understanding of Elixir language and its ecosystem?

Have they demonstrated an ability to write efficient and clean Elixir code?

Are they familiar with Erlang and BEAM?

Do they have experience with concurrency and multi-threading?

Next 20 minutes

Specific Elixir Native Implemented Functions 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 are some best practices for writing NIFs?

Some best practices include: keeping NIFs short to avoid blocking the scheduler, checking for errors and returning appropriate error tuples, using Erlang's memory management functions, and testing NIFs thoroughly to avoid crashes.

How would you handle long-running computations in a NIF?

Long-running computations should be offloaded to a separate thread or process to avoid blocking the Erlang scheduler. The Dirty Scheduler feature of the Erlang VM can also be used to run long-running NIFs.

Describe the difference between dirty and regular NIFs.

Regular NIFs are expected to return quickly, while dirty NIFs can run for a long time without returning. Dirty NIFs are run on separate scheduler threads, so they don't block the main scheduler.

What are some use cases for using NIFs in Elixir?

NIFs are useful for performance-critical code, for interfacing with external libraries written in other languages, and for accessing OS-level functionality that is not available in Elixir or Erlang.

How would you handle errors in a NIF?

Errors in a NIF can be handled by returning an error tuple from the NIF. The Erlang NIF API also provides functions for raising exceptions from within a NIF.

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At this point, a skilled Elixir Native Implemented Functions engineer should demonstrate strong problem-solving abilities, proficiency in Elixir Native Implemented Functions 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 Native Implemented Functions.

What does this simple Elixir function do?
defmodule Example do
  def add(a, b) do
    a + b
  end
end
This function adds two numbers together. It's defined inside a module named 'Example'.
What will be the output of this Elixir code?
defmodule Example do
  def print_type(x) when is_integer(x), do: IO.puts("Integer")
  def print_type(x) when is_float(x), do: IO.puts("Float")
end

Example.print_type(10)
Example.print_type(10.5)
This code will print 'Integer' when the input is an integer and 'Float' when the input is a float. So, the output will be 'Integer' followed by 'Float'.
What does this Elixir code do with a list?
defmodule Example do
  def sum_list(list) do
    Enum.reduce(list, 0, &(&1 + &2))
  end
end

Example.sum_list([1, 2, 3, 4, 5])
This code sums all the elements of a list. The 'Enum.reduce' function is used to iterate over the list and add each element to the accumulator, which is initially 0.
What does this Elixir code do with concurrency?
defmodule Example do
  def create_task(fun) do
    Task.async(fun)
  end
end

Example.create_task(fn -> 1 + 2 end)
This code creates a new task that will execute the given function in a separate process. The 'Task.async' function is used to start the process. The function will add 1 and 2 together.

Wrap-up questions

Final candidate for Elixir Native Implemented Functions 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 Native Implemented Functions application deployments. Inquire about their experience in handling system failures and their approach to debugging and troubleshooting.

What are the steps to interface a C library with Elixir using NIFs?

First, you would write a C function that wraps the library function you want to call. Then, you would write a NIF that calls this wrapper function. Finally, you would compile the C code into a shared library and load it into Elixir using the :erlang.load_nif function.

How would you ensure that a NIF doesn't block the Erlang scheduler?

You can ensure this by keeping the NIF short and returning quickly. If the NIF needs to do a long-running computation, it should offload the computation to a separate thread or process, or use the Dirty Scheduler feature of the Erlang VM.

Describe the difference between using NIFs and using C Node in Elixir.

NIFs and C Nodes are both ways to interface with C code from Elixir, but they work in different ways. NIFs are functions that run in the same memory space as the Erlang VM, while C Nodes are separate Erlang nodes that run in their own OS process and communicate with the Elixir code over the network.

Elixir Native Implemented Functions application related

Product Perfect's Elixir Native Implemented Functions development capabilities

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

Elixir Native Implemented Functions Consultive assessments

Elixir Native Implemented Functions Application Conversion Assessment Elixir Native Implemented Functions Application Integration Assessment Elixir Native Implemented Functions Data & Database Integration Assessment

Custom Elixir Native Implemented Functions development projects

Custom Elixir Native Implemented Functions App Conversion Elixir Native Implemented Functions Custom App Development Process App UI Design for Elixir Native Implemented Functions Facelifts

Hiring guide for Elixir Native Implemented Functions Engineers

Elixir Native Implemented Functions Developer Hiring Guide

What you’re looking for early on

The ideal back-end app developer

What you’re looking to see on the Elixir Native Implemented Functions engineer at this point.

Elixir Native Implemented Functions Consultive assessments

Custom Elixir Native Implemented Functions development projects