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* Opa is a statically typed, object-oriented programming language designed for rapid application development. * It was created by Peter Van Roy and Yves R. Meyer in 1987. * Opa is based on ML, and features a number of modern language features such as generics, closures, and pattern matching. * Opa is open source software, and is available under the Apache License 2.0. * Opa is used by a number of companies, including Google, Facebook, and Amazon.

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

First 20 minutes

General Opa app knowledge and experience

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

How would you define Opa?

Opa is a high-level, statically-typed programming language for developing web applications. It is a full-stack language, meaning it is designed to handle both the client-side and server-side parts of a web application.

What are the key features of Opa?

Opa has several key features including strong static typing, automatic memory management, native support for web standards like HTML, CSS and JavaScript, and a powerful type inference system.

Describe the difference between Opa and JavaScript.

While both are used for web development, Opa is a full-stack language, meaning it can handle both the client-side and server-side parts of a web application. JavaScript, on the other hand, is primarily a client-side language, though it can also be used on the server-side with Node.js.

How would you handle error handling in Opa?

Opa has a built-in exception handling mechanism. You can use the 'try...catch' construct to catch exceptions and handle them appropriately.

What are the advantages of using Opa for web development?

Opa offers several advantages for web development, including strong static typing, automatic memory management, native support for web standards, and a powerful type inference system. It also eliminates the need to use multiple languages for different parts of a web application.

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What you’re looking for early on

Does the candidate demonstrate a strong understanding of Opa programming language?

Has the candidate shown experience with web development?

Can the candidate effectively communicate their thought process and problem-solving approach?

Is the candidate familiar with the full-stack development process?

Next 20 minutes

Specific Opa 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 implement a RESTful API in Opa?

In Opa, you can define a RESTful API using the 'resource' keyword. You can then define the different HTTP methods (GET, POST, PUT, DELETE) for that resource.

What is the role of the Opa compiler?

The Opa compiler is responsible for translating Opa code into JavaScript and Node.js code. This allows Opa applications to run on any platform that supports JavaScript and Node.js.

Describe the difference between Opa and Node.js.

Opa is a full-stack language designed for web development, while Node.js is a runtime environment that allows JavaScript to be used on the server-side. Opa code is compiled into JavaScript and Node.js code, allowing it to run on any platform that supports these technologies.

How would you handle database operations in Opa?

Opa has built-in support for MongoDB, a popular NoSQL database. You can use the 'db' keyword to define a database, and then use Opa's database API to perform operations like insert, update, delete and query.

What are the disadvantages of using Opa for web development?

While Opa has many advantages, it also has some disadvantages. These include a smaller community compared to other languages, less third-party library support, and the need to learn a new language for developers already familiar with traditional web development languages.

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

What does the following simple Opa code do?
function start() {
  Server.start(Server.http, { title: 'Hello', page: function() { Hello, world! } })
}
This code starts a simple HTTP server that responds to all requests with a page containing the text 'Hello, world!' inside a level 1 heading.
What does the following Opa syntax do?
function add(x, y) { x + y }
This code defines a function named 'add' that takes two arguments, 'x' and 'y', and returns their sum.
What does the following Opa code do with an array?
function sum(arr) { List.fold(function(x, acc) { x + acc }, 0, arr) }
This code defines a function named 'sum' that takes an array 'arr' and returns the sum of all its elements. It uses the 'List.fold' function to iterate over the array and accumulate the sum.
What does the following Opa code do related to threading or concurrency?
function async_add(x, y, cb) { Thread.start(function() { cb(x + y) }) }
This code defines a function named 'async_add' that takes two arguments, 'x' and 'y', and a callback function 'cb'. It starts a new thread to calculate the sum of 'x' and 'y', and then calls the callback function with the result.

Wrap-up questions

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

How would you handle user authentication in Opa?

Opa has built-in support for user authentication. You can use the 'user' keyword to define a user, and then use Opa's authentication API to handle user registration, login, and session management.

Describe the difference between Opa and traditional web development languages like PHP or Ruby.

Opa is a full-stack language, meaning it can handle both the client-side and server-side parts of a web application. Traditional web development languages like PHP or Ruby are primarily used on the server-side, with separate languages (like JavaScript) used on the client-side.

How would you handle real-time communication in Opa?

Opa has built-in support for real-time communication using WebSockets. You can use the 'websocket' keyword to define a WebSocket, and then use Opa's WebSocket API to handle communication between the client and server.

Opa application related

Product Perfect's Opa development capabilities

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

Opa Consultive assessments

Opa Application Conversion Assessment Opa Application Integration Assessment Opa Data & Database Integration Assessment

Custom Opa development projects

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

Hiring guide for Opa Engineers

Opa Developer Hiring Guide

What you’re looking for early on

The ideal back-end app developer

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

Hello, world!

Opa Consultive assessments

Custom Opa development projects