Back-End Developer Interview Questions

A list of helpful back-end related questions you can use to interview potential candidates. Inspired by the git-repo: https://github.com/darcyclarke/Front-end-Developer-Interview-Questions.git and Paul Irish (@paul_irish)

@Version 1.0.1

This repo contains a number of back-end interview questions that can be used when vetting potential candidates. It is by no means recommended to use every single question here on the same candidate (that would take hours). Choosing a few items from this list should help you vet the intended skills you require.

Note: Keep in mind that many of these questions are open ended and could lead to interesting discussions that tell you more about the person's capabilities than a straight answer would.

Table of Contents

• Contributors
• General Questions
• Design Pattern Specific Questions
  • MVC
  • MVVM
  • Repository
  • Dependency Injection
  • Visitor
• PHP Code examples
• PHP Specific Questions
• Database Specific Questions
• ORM Specific Questions
  • Doctrine
• HTTP Specific Questions
• Operating System Specific Questions
• Web Services Specific Questions
  • Common Server Response Codes
• Network Specific Questions

Contributors

• @travisvandame
• @jmurowaniecki
• @emanuelsaringan

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General Questions

1. What did you learn yesterday/this week?
2. What excites or interests you about coding?
3. What version control systems have you used (Git, SVN etc.)?
4. What is your preferred development environment? (OS, Editor, Browsers, Tools etc.)
5. How do you go about testing your PHP?
6. Have you ever looked at the source code of the libraries/frameworks you use?
7. How do you organize your code?
8. When do you optimize your code?
9. If you could master one technology this year what would it be?
10. Explain the importance of standards and standards bodies.
11. Explain MVC, HMVC, the differences, goals and cons.
12. What did you learn/know about agile methodology?
13. Do you prefer to work on a team or alone?
14. What's the biggest problem faced on your projects and how did you solve it?
15. How you contribute to the open source community (Github, Bitbucket, IRC, forums)?
16. What do you think about algorithms? An algorithm which you like. Discuss.

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Design Pattern Specific Questions

• MVC
  • Question: In the MVC design pattern what's M stands for? Answer: M stands for Model, it is the data and data-management of the application.
• MVVM
• Repository
• Dependency Injection
• Visitor
  • The classes and/or objects participating in this pattern are? Answer: Visitor, ConcreteVisitor, Element, ConcreteElement, ObjectStructure

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PHP Code Examples:

floor(3.14)

Question: What value is returned from the above statement? Answer: 3

echo join("", array_reverse(str_split("i'm a lasagna hog")));

Question: What value is returned from the above statement? Answer: "goh angasal a m'i"

$array = array();

array_push($array, 1);
array_push($array, 2);

Question: What is the value of count($array)? Answer: 2

$foo = "Hello";

function alert_a() {
	global $foo;

	$bar = " World";

	echo ($foo . $bar);
}

function alert_b() {
	$bar = " World";

	echo ($foo . $bar);
}

alert_a();
alert_b();

Question: What is the outcome of the two alerts above? Answer: alert_a() = Hello World, alert_b() = E_NOTICE : type 8 -- Undefined variable: foo -- at line 15 World

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###PHP Specific Questions

• Describe two good uses - and practices - for callback usage.

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Database Specific Questions

• General SQL
  • What is the difference between a View and a Table?
  • What does the HAVING clause do?
  • How do you choose a column to be indexed?
• Do you know MySQL?
  • How would you backup and restore data using mysqldump from the command line?
  • When should you use SQL_CACHE and S_NO_CACHE on your queries?
  • Question: describe five functions that disable cache on queries and describe why. Answer: BENCHMARK(), CONNECTION_ID(), CONVERT_TZ(), CURDATE(), CURRENT_DATE(), CURRENT_TIME(), CURRENT_TIMESTAMP(), CURTIME(), DATABASE(), ENCRYPT(), with one parameter FOUND_ROWS(), GET_LOCK(), LAST_INSERT_ID(), LOAD_FILE(), MASTER_POS_WAIT(), NOW(), RAND(), RELEASE_LOCK(), SLEEP(), SYSDATE(), UNIX_TIMESTAMP(), USER(), UUID(), UUID_SHORT()
  • Have you tinkered with MySQL server optimization, and if so, what did you do to alleviate what problems?
• Do you know PostgreSQL?
  • How do you improve Resource Consumption?
• SQL Server
  • How would you migrate from SQL Server to PostgreSQL or MySQL?
• Do you know How to 'hack', build a cluster, improve performance, implement cache, pooling or compile those services from source?
• Are you familiar with NoSQL databases?

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HTTP Specific Questions

• What happens between the time you enter a URL in your browser until you see the page that you requested?
• How does the 3-way TCP handshake occur when you request a page from a server?
• What are the contents of an HTTP request header? Response header?
• What is the difference between HTTP and HTTPS?
• How would you design a URL shortener similar to bit.ly?

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ORM Specific Questions

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Web Services Specific Questions

• Have you created or managed some web service?
• What web service protocols do you know?

Common Server Response Codes

Question: Describe server response code 200. Answer: ("OK") Everything went ok. The entity-body, if any, is a representation of some resource.

Question: Describe server response code 201. Answer: ("Created") A new resource was created at the client's request. The location header should contain a URI to the new resource and the entity-body should contain a representation of the newly created resource.

Question: Describe server response code 204. Answer: ("No Content") The server declined to send back any status message or representation

Question: Describe server response code 301. Answer: ("Moved Permanently") Client triggered an action on the server that caused the URI of a resource to change.

Question: Describe server response code 400. Answer: ("Bad Request") A problem occurred on the client side. The entity-body, if any, is a error message.

Question: Describe server response code 401. Answer: ("Unauthorized") The client failed to provide proper authentication for the requested resource.

Question: Describe server response code 404. Answer: ("Not Found") Client requested a URI that doesn't map to any resource.

Question: Describe server response code 409. Answer: ("Conflict") Client attempted to put the servers resource into a impossible or inconsistent state.

Question: Describe server response code 500 Answer: ("Internal Server Error") A problem occurred on the server side. The entity-body, if any, is a error message.

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Operating System Specific Questions

• Linux/Unix/MacOS
  • Do you know how to use MacPorts, Aptitude, YUM, RPM and other package managers?
  • How often do you update running services?
  • How would you install, configure and handle services such nginx, apache, squid, samba, etc..?
  • What do you know about kernel tuning?
  • What do you know about virtualization?
  • What is the difference between threads and processes?
• Microsoft
  • How to remove Windows?
  • How would you install Linux using USB or liveCDs?
  • How would you disable Secure Boot and install Linux?
  • How would you migrate from windows to Linux?

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Network Specific Questions

• What are the 7 layers of the OSI model?
• What are some advantages of CDNs? Disadvantages?
• What is a reverse proxy?
• What ports do the following use?
  • HTTP
  • HTTPS
  • SSH

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