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Elixir Streams is a functional, concurrent, general-purpose programming language that runs on the Erlang virtual machine (BEAM). Developed by José Valim in 2011, it was designed to be scalable and maintainable, enabling the development of high-quality, fault-tolerant systems. Elixir's Streams module provides lazy computation capabilities, allowing for potentially infinite data processing. The language's syntax is heavily influenced by Ruby, while its concurrency model is derived from Erlang. Elixir is widely used in web development, embedded software, data ingestion, and multimedia processing pipelines.

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

First 20 minutes

General Elixir Streams app knowledge and experience

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

What are the main uses of Elixir Streams?

Elixir Streams are mainly used for lazy evaluation, handling large data processing, and for creating potentially infinite data structures.

How would you create a simple Elixir Stream?

You can create a simple Elixir Stream using the Stream module. For example, Stream.cycle([1, 2, 3]) will create a stream that cycles through the numbers 1, 2, and 3 indefinitely.

Describe the difference between Elixir Streams and Elixir Lists.

The main difference is that Elixir Lists are eager and Streams are lazy. This means that Lists compute their values immediately, while Streams compute their values only when they are needed.

What are the benefits of using Elixir Streams over Elixir Lists?

The main benefits of using Elixir Streams over Lists are memory efficiency and the ability to handle infinite data structures. Since Streams are lazily evaluated, they only consume memory when needed.

How would you use the Stream.map function in Elixir?

The Stream.map function is used to apply a function to each element in a stream. For example, Stream.map([1, 2, 3], &(&1 * 2)) would return a new stream with the numbers 2, 4, and 6.

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What you’re looking for early on

Does the candidate demonstrate a deep understanding of Elixir Streams?

Has the candidate shown experience with concurrent and distributed systems?

Can the candidate effectively troubleshoot and debug Elixir code?

Does the candidate show good problem-solving skills?

Next 20 minutes

Specific Elixir Streams 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 purpose of the Stream.cycle function in Elixir?

The Stream.cycle function is used to create a stream that endlessly repeats a given enumerable. For example, Stream.cycle([1, 2, 3]) would create a stream that cycles through the numbers 1, 2, and 3 indefinitely.

How would you handle exceptions in Elixir Streams?

Exceptions in Elixir Streams can be handled using the try/rescue construct. You would use try to wrap the code that might raise an exception, and rescue to catch and handle the exception.

What is the difference between Stream.filter and Stream.reject in Elixir?

Stream.filter and Stream.reject are both used to filter elements in a stream. Stream.filter returns a stream with elements for which the function returns true, while Stream.reject returns a stream with elements for which the function returns false.

How would you create a stream that generates an infinite sequence of Fibonacci numbers in Elixir?

You can create such a stream using the Stream.unfold function. The initial state would be {0, 1}, and the function would return the current Fibonacci number and the next state {b, a + b}.

What is the purpose of the Stream.take function in Elixir?

The Stream.take function is used to return the first n elements from a stream. For example, Stream.take(Stream.cycle([1, 2, 3]), 5) would return the list [1, 2, 3, 1, 2].

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

What does this simple Elixir Streams code do?
stream = Stream.map([1, 2, 3, 4, 5], fn x -> x * 2 end)
Enum.to_list(stream)
This code creates a stream from a list of numbers and applies a function to each element that multiplies it by 2. The stream is then converted back to a list. The output will be a list of the original numbers, each multiplied by 2.
What will be the output of this Elixir Streams code?
stream = Stream.iterate(2, &(&1 * 2))
Enum.take(stream, 5)
This code creates a stream that starts at 2 and each subsequent element is the previous element multiplied by 2. It then takes the first 5 elements from the stream. The output will be a list: [2, 4, 8, 16, 32].
What does this Elixir Streams code do with a collection?
stream = Stream.filter([1, 2, 3, 4, 5, 6], fn x -> rem(x, 2) == 0 end)
Enum.to_list(stream)
This code creates a stream from a list of numbers and applies a function to each element that checks if it is even. The stream is then converted back to a list. The output will be a list of the even numbers from the original list.
What does this Elixir Streams code do related to concurrency?
stream = Stream.cycle([1, 2, 3])
Enum.take(stream, 10)
This code creates a stream that cycles through the elements of the list [1, 2, 3] indefinitely. It then takes the first 10 elements from the stream. The output will be a list: [1, 2, 3, 1, 2, 3, 1, 2, 3, 1].

Wrap-up questions

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

How would you use the Stream.drop function in Elixir?

The Stream.drop function is used to skip the first n elements from a stream. For example, Stream.drop(Stream.cycle([1, 2, 3]), 5) would return a stream that starts with the number 3.

What is the difference between Stream.flat_map and Stream.map in Elixir?

Stream.flat_map and Stream.map are both used to apply a function to each element in a stream. The difference is that Stream.flat_map flattens the result into the output stream, while Stream.map does not.

How would you use the Stream.concat function in Elixir?

The Stream.concat function is used to concatenate two or more streams into a single stream. For example, Stream.concat([1, 2, 3], [4, 5, 6]) would return a stream with the numbers 1 to 6.

Elixir Streams application related

Product Perfect's Elixir Streams development capabilities

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

Elixir Streams Consultive assessments

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

Custom Elixir Streams development projects

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

Hiring guide for Elixir Streams Engineers

Elixir Streams 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 Streams engineer at this point.

Elixir Streams Consultive assessments

Custom Elixir Streams development projects