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Lua is a powerful, efficient, lightweight, and embeddable scripting language, first developed in 1993 by Roberto Ierusalimschy, Luiz Henrique de Figueiredo, and Waldemar Celes at the Pontifical Catholic University of Rio de Janeiro, Brazil. It was designed with a focus on simplicity, small size, and portability with extensible semantics. Lua's design is noted for its minimalism and flexibility, often used for scripting in games and web applications. It is cross-platform, with interpreters available for various operating systems. Lua's popularity in the gaming industry is exemplified by its adoption in major titles like World of Warcraft and Angry Birds.

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

First 20 minutes

General Lua app knowledge and experience

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

How would you declare a variable in Lua?

You can declare a variable in Lua using the local keyword followed by the variable name. For example, 'local x'.

What are the basic data types in Lua?

The basic data types in Lua are nil, boolean, number, string, userdata, function, thread, and table.

How would you create a function in Lua?

You can create a function in Lua using the function keyword. For example, 'function myFunction() end'.

What is the difference between local and global variables in Lua?

Local variables have their scope limited to the block where they are declared. Global variables don't have a specific scope and can be accessed from anywhere in the code.

How would you implement error handling in Lua?

Error handling in Lua can be implemented using the pcall function, which executes a function in protected mode and catches any errors.

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What you’re looking for early on

Does the candidate have a strong understanding of the Lua programming language?

Has the candidate demonstrated problem-solving skills during the interview?

Can the candidate work well in a team environment?

Does the candidate have experience with Lua libraries and frameworks?

Next 20 minutes

Specific Lua 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 metatables in Lua?

Metatables in Lua are tables that can change the behavior of the original table. They can define how an object behaves in arithmetic operations, comparisons, concatenation, length operation, etc.

Describe the difference between pairs and ipairs in Lua.

Pairs iterates over all elements in the table, while ipairs iterates only over the integer indexes of a table.

How would you create a table in Lua?

You can create a table in Lua using the {} syntax. For example, 'local myTable = {}'.

What is the use of the '#' operator in Lua?

The '#' operator is used to get the length of a string or the number of elements in a table.

How would you implement inheritance in Lua?

Inheritance in Lua can be implemented using metatables. The metatable of the derived class points to the base class, allowing the derived class to access the base class's methods.

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

What does the following Lua code do?
print(type('Hello world'))
This code prints the type of 'Hello world', which is a string.
What will be the output of the following Lua code?
x = 10
y = 20
print(x == y)
The code compares the values of x and y. Since 10 is not equal to 20, it will print 'false'.
What does the following Lua code do?
t = {4, 5, 6}
table.insert(t, 1, 3)
print(t[1])
This code creates a table (array) 't' with elements 4, 5, 6. Then it inserts the number 3 at the first position of the table. Finally, it prints the first element of the table, which is 3.
What does the following Lua code do?
co = coroutine.create(function () print('hello') end)
coroutine.resume(co)
This code creates a coroutine that prints 'hello' when it is resumed. The coroutine is then resumed, so it will print 'hello'.

Wrap-up questions

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

What are coroutines in Lua?

Coroutines are a kind of lightweight threads that don't share state with other coroutines. They are used for non-preemptive multitasking.

Describe the difference between the '==' and '===' operators in Lua.

Lua only has the '==' operator for equality comparison. The '===' operator does not exist in Lua.

How would you write a recursive function in Lua?

A recursive function in Lua is a function that calls itself. For example, a function to calculate the factorial of a number could be written recursively.

Lua application related

Product Perfect's Lua development capabilities

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

Lua Consultive assessments

Lua Application Conversion Assessment Lua Application Integration Assessment Lua Data & Database Integration Assessment

Custom Lua development projects

Custom Lua App Conversion Lua Custom App Development Process App UI Design for Lua Facelifts

Hiring guide for Lua Engineers

Lua Developer Hiring Guide

What you’re looking for early on

The ideal back-end app developer

What you’re looking to see on the Lua engineer at this point.

Lua Consultive assessments

Custom Lua development projects