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TOML, or Tom's Obvious, Minimal Language, is a configuration file format that is easy to read due to its clear and simple syntax. It was introduced by Tom Preston-Werner, a co-founder of GitHub, in 2013 as a more human-friendly alternative to formats like JSON and YAML. TOML is designed to map unambiguously to a hash table, making it ideal for data serialization. It is widely used in various software projects, including Rust's package manager, Cargo. The official specification for TOML can be found on GitHub, where it continues to be actively maintained and developed.

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

First 20 minutes

General TOML app knowledge and experience

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

How would you define TOML?

TOML is a configuration file format that is easy to read and write. It stands for Tom's Obvious, Minimal Language and is used for configuration files.

What are the basic types supported by TOML?

TOML supports basic types such as String, Integer, Float, Boolean, Datetime, Array, and Table.

How would you represent a date in TOML?

Dates in TOML can be represented in RFC 3339 format. For example, 1979-05-27T07:32:00Z.

Describe the difference between TOML and JSON.

TOML is more human-readable and easier to write than JSON. However, JSON is more popular and has wider support in programming languages.

How would you represent a nested object in TOML?

Nested objects in TOML can be represented using tables. For example, [table.subtable].

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What you’re looking for early on

Does the candidate have a strong understanding of TOML syntax and structure?

Has the candidate demonstrated experience with using TOML in real-world projects?

Can the candidate troubleshoot and debug TOML files?

Is the candidate familiar with the latest TOML version and its features?

Next 20 minutes

Specific TOML 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 use of arrays in TOML and how are they represented?

Arrays in TOML are used to group multiple values together. They are represented within square brackets. For example, arr = [1, 2, 3].

How would you comment in TOML?

Comments in TOML can be added using the # symbol. Anything after this symbol on the same line is considered a comment.

What are the rules for keys in TOML?

Keys in TOML must be on the same line as the equals sign and they must either be bare, quoted, or dotted.

How would you represent a string in TOML?

Strings in TOML are represented within double quotes. For example, str = "Hello, World!".

What is the use of tables in TOML?

Tables in TOML are used to group related values. They are represented within square brackets. For example, [table].

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

What does this simple TOML code represent?
[servers]
  [servers.alpha]
  ip = "10.0.0.1"
  dc = "eqdc10"
  [servers.beta]
  ip = "10.0.0.2"
  dc = "eqdc10"
This TOML code represents a configuration for two servers: alpha and beta. Each server has its own IP address and data center(dc).
What does this TOML code represent and what is its equivalent in JSON?
[fruit]
  [[fruit.apple]]
  name = "red delicious"
  [[fruit.apple]]
  name = "granny smith"
This TOML code represents a collection of apples under the fruit category. Each apple has a name. The equivalent JSON would be: {'fruit': {'apple': [{'name': 'red delicious'}, {'name': 'granny smith'}]}}
What will be the output of this TOML code?
[clients]
  data = [ ["gamma", "delta"], [1, 2] ]
This TOML code represents a configuration for a 'clients' section where 'data' is an array of arrays. The first array contains strings while the second array contains integers.
What does this TOML code do?
[database]
  server = "192.168.1.1"
  ports = [ 8001, 8001, 8002 ]
  connection_max = 5000
  enabled = true
This TOML code represents a configuration for a database. It specifies the server's IP address, the ports, the maximum number of connections, and whether the database is enabled.

Wrap-up questions

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

How would you represent a boolean in TOML?

Booleans in TOML are represented as true or false. For example, bool = true.

What are the rules for values in TOML?

Values in TOML must be of a certain type and they must be on the same line as the equals sign and key.

How would you represent an integer in TOML?

Integers in TOML are represented as normal numbers without quotes. For example, int = 123.

TOML application related

Product Perfect's TOML development capabilities

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

TOML Consultive assessments

TOML Application Conversion Assessment TOML Application Integration Assessment TOML Data & Database Integration Assessment

Custom TOML development projects

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

Hiring guide for TOML Engineers

TOML Developer Hiring Guide

What you’re looking for early on

The ideal back-end app developer

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

TOML Consultive assessments

Custom TOML development projects