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Elixir Protocols is a dynamic, functional language designed for building scalable and maintainable applications. It was developed by José Valim in 2011, who aimed to create a language that would be concurrent, fault-tolerant and distributed. Elixir leverages the Erlang VM, known for running low-latency, distributed systems. Protocols are a mechanism to achieve polymorphism in Elixir; they allow developers to define functions that can operate on multiple data types. As an open-source project, it has been widely adopted across various industries due to its robustness and versatility.

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

First 20 minutes

General Elixir Protocols app knowledge and experience

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

What are Elixir Protocols?

Elixir Protocols are a mechanism for achieving polymorphism in Elixir. They allow developers to define a function or a set of functions and then implement them for any data type.

How would you define a protocol in Elixir?

In Elixir, a protocol can be defined using the 'defprotocol' keyword followed by the name of the protocol and do block. Inside the do block, you can define the functions for the protocol.

How would you implement a protocol for a specific data type in Elixir?

You can implement a protocol for a specific data type using the 'defimpl' keyword followed by the name of the protocol, the 'for' keyword and the data type. Inside the do block, you can provide the implementation for the protocol's functions.

What is the purpose of the '__using__' macro in Elixir protocols?

The '__using__' macro in Elixir protocols is used to inject code in the module that is using the protocol. This can be used to provide default implementations for the protocol's functions.

Describe the difference between protocols and behaviours in Elixir.

Behaviours in Elixir are a way to define a contract that modules need to follow, while protocols are a mechanism to achieve polymorphism. Protocols allow you to define a set of functions and implement them for any data type, whereas behaviours require you to implement all the functions in the contract.

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What you’re looking for early on

Does the candidate have a clear understanding of Elixir Protocols?

How proficient is the candidate in using Elixir for software development?

Can the candidate demonstrate a good understanding of functional programming concepts?

Is the candidate able to solve problems and debug issues effectively?

Next 20 minutes

Specific Elixir Protocols 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.

How would you use the 'Any' protocol in Elixir?

The 'Any' protocol in Elixir is a fallback protocol that is used when no specific implementation is found for a data type. You can use it to provide a generic implementation for a function that can work with any data type.

How can you check if a data type implements a certain protocol in Elixir?

You can use the 'Protocol.consolidated?' function in Elixir to check if a data type implements a certain protocol. This function takes the protocol and the data type as arguments and returns true if the data type implements the protocol, and false otherwise.

What is protocol consolidation in Elixir?

Protocol consolidation is a process in Elixir that makes protocol dispatch faster. It generates a single module for each protocol-data type pair at compile time, which speeds up the lookup of the correct implementation.

How would you consolidate protocols in Elixir?

You can consolidate protocols in Elixir using the 'mix compile.protocols' task. This task will consolidate all protocols into a single module for each protocol-data type pair.

What is the difference between static and dynamic dispatch in Elixir protocols?

Static dispatch in Elixir protocols happens at compile time, where the correct implementation of a function for a data type is determined. Dynamic dispatch, on the other hand, happens at runtime, where the correct implementation is looked up based on the actual data type of the value.

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

What does this simple Elixir code do?
IO.puts "Hello, World!"
This code prints the string 'Hello, World!' to the console.
What does the following Elixir code do?
defmodule Math do
  def add(a, b), do: a + b
end
This code defines a module named 'Math' with a function 'add' that takes two parameters and returns their sum.
What will be the output of this Elixir code?
list = [1, 2, 3, 4]
Enum.map(list, fn x -> x * 2 end)
This code multiplies each element in the list by 2. The output will be a new list: [2, 4, 6, 8].
What does this Elixir code do?
spawn(fn -> 1 + 2 end)
This code spawns a new process that executes the function, which adds 1 and 2. However, the result of the function is not used or stored anywhere.

Wrap-up questions

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

How would you handle unknown data types in Elixir protocols?

In Elixir protocols, unknown data types can be handled by providing an implementation for the 'Any' protocol. This will serve as a fallback for any data type that doesn't have a specific implementation.

What are the benefits of using protocols in Elixir?

Protocols in Elixir provide a way to achieve polymorphism, which allows you to write more flexible and reusable code. They also allow you to extend the functionality of existing data types without modifying their code.

How would you implement a protocol for a custom data type in Elixir?

You can implement a protocol for a custom data type in Elixir in the same way as for built-in data types. You use the 'defimpl' keyword followed by the name of the protocol, the 'for' keyword and the custom data type. Inside the do block, you provide the implementation for the protocol's functions.

Elixir Protocols application related

Product Perfect's Elixir Protocols development capabilities

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

Elixir Protocols Consultive assessments

Elixir Protocols Application Conversion Assessment Elixir Protocols Application Integration Assessment Elixir Protocols Data & Database Integration Assessment

Custom Elixir Protocols development projects

Custom Elixir Protocols App Conversion Elixir Protocols Custom App Development Process App UI Design for Elixir Protocols Facelifts

Hiring guide for Elixir Protocols Engineers

Elixir Protocols 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 Protocols engineer at this point.

Elixir Protocols Consultive assessments

Custom Elixir Protocols development projects