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Elixir is a dynamic, functional language designed for building scalable and maintainable applications. It leverages the Erlang VM, known for running low-latency, distributed, and fault-tolerant systems. Introduced in 2011 by José Valim, Elixir provides extensible design and meta-programming capabilities that enable the development of domain-specific languages. Its built-in support for handling date and time makes it a preferred choice for time-critical applications. Elixir's robust tooling and rich ecosystem have made it a popular choice among developers and businesses worldwide.

Ask the right questions secure the right Elixir Date and Time talent among an increasingly shrinking pool of talent.

First 20 minutes

General Elixir Date and Time app knowledge and experience

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

What is the use of DateTime module in Elixir?

DateTime is a module in Elixir that provides functions for working with dates and times. It allows us to create, manipulate, format and parse dates and times.

How would you create a new DateTime instance in Elixir?

You can create a new DateTime instance using the `DateTime.new/2` function. You would pass in a date and a time, and optionally a time zone.

What is the difference between DateTime.utc_now and DateTime.now in Elixir?

`DateTime.utc_now` returns the current date and time in UTC, while `DateTime.now` returns the current date and time in the local time zone.

How would you format a DateTime object in Elixir?

You can use the `DateTime.to_string/1` function to format a DateTime object. This function returns a string in the ISO 8601 date format.

How would you parse a DateTime string in Elixir?

You can use the `DateTime.from_iso8601/1` function to parse a DateTime string. This function takes a string in the ISO 8601 date format and returns a DateTime struct.

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What you’re looking for early on

Does the candidate demonstrate a strong understanding of Elixir and its syntax?

Has the candidate shown proficiency in handling Date and Time data types in Elixir?

Is the candidate familiar with Elixir libraries and frameworks relevant to Date and Time manipulation?

How well does the candidate understand concurrent and distributed computing?

Next 20 minutes

Specific Elixir Date and Time 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 the uses of Date module in Elixir?

The Date module in Elixir provides functions for creating, formatting, and manipulating dates. It does not deal with times or time zones.

Describe the difference between Date and DateTime in Elixir.

In Elixir, Date deals only with dates, it does not include time or timezone information. DateTime, on the other hand, includes both date and time, and also includes timezone information.

How would you subtract two dates in Elixir?

You can subtract two dates in Elixir by converting them to Unix timestamps using the `Date.to_unix/1` function, subtracting the timestamps, and then converting the result back to a Date using the `Date.from_unix/1` function.

What is the use of NaiveDateTime module in Elixir?

NaiveDateTime is a module in Elixir that provides functions for working with dates and times without time zone information. It's 'naive' in the sense that it's not aware of time zones.

How would you convert a DateTime to a NaiveDateTime in Elixir?

You can convert a DateTime to a NaiveDateTime using the `DateTime.to_naive/1` function. This function returns a NaiveDateTime struct that has the same date and time as the original DateTime, but without time zone information.

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

What does the following simple Elixir code do?
{:ok, date} = Date.new(2022, 2, 20)
This code creates a new Date struct for 20th February 2022. The :ok atom indicates the operation was successful.
What is the output of the following Elixir code?
IO.inspect Date.day_of_week(~D[2022-02-20])
The output will be 7. The Date.day_of_week function returns the day of the week as an integer (1 for Monday, 7 for Sunday) for the given date.
What does this Elixir code do?
dates = Enum.map(1..5, fn i -> Date.add(~D[2022-02-20], i) end)
This code creates a list of dates starting from 20th February 2022 and adds 1 to 5 days to it. The Enum.map function is used to transform the range 1..5 into a list of dates.
What does the following Elixir code do?
Task.async(fn -> Date.utc_today() end)
This code creates a new asynchronous task that will execute the function to get today's date in UTC. The Task.async function is used for concurrency in Elixir.

Wrap-up questions

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

What's the difference between DateTime.to_unix and DateTime.to_iso8601 in Elixir?

`DateTime.to_unix/1` converts a DateTime to a Unix timestamp, which is a number representing the number of seconds since January 1, 1970. `DateTime.to_iso8601/1`, on the other hand, converts a DateTime to a string in the ISO 8601 date format.

How would you add a duration to a DateTime in Elixir?

You can add a duration to a DateTime using the `DateTime.add/3` function. This function takes a DateTime, a number of seconds to add, and an optional unit of time (default is :second).

What is the purpose of Time module in Elixir?

The Time module in Elixir provides functions for creating, formatting, and manipulating times. It does not deal with dates or time zones.

Elixir Date and Time application related

Product Perfect's Elixir Date and Time development capabilities

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

Elixir Date and Time Consultive assessments

Elixir Date and Time Application Conversion Assessment Elixir Date and Time Application Integration Assessment Elixir Date and Time Data & Database Integration Assessment

Custom Elixir Date and Time development projects

Custom Elixir Date and Time App Conversion Elixir Date and Time Custom App Development Process App UI Design for Elixir Date and Time Facelifts

Hiring guide for Elixir Date and Time Engineers

Elixir Date and Time 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 Date and Time engineer at this point.

Elixir Date and Time Consultive assessments

Custom Elixir Date and Time development projects