Confluent Onsite | India

Recruiter reached out on linkedin.

Phone:

• Given a list of doc and a query string, return which documents contain the query string in it.

Input:

[][]string{
{"this", "is", "world"}, 
{"world", "is", "great"}, 
{"leetcode", "is", "bad"} 
}

query("World") --> should return [0,1] (make sure your search is case insensitve)

follow up:

Search the document where given phrase is present

query("word is") --> should return [1] since it is only present in doc 1

Onsite 1:

• Sudoku validation
• Sudoku completion

Onsite 2:

• Design a queue that support enqueue, dequeue and getRandom() operations.
• Follow up included concurrency.
  What will happen if multiple threads are working together?
  What are the solutions available to support multiple threads?
• Write method to compare two given queues.
  Again, follow ups were about support concurrency in this method.
• Write UTs for the enqueue, dequeue and getRandom(). They just wanted to get idea about UT techniques.

I was asked to run the code (interviewer provided the test cases) in phone screen and 1st onsite. Wasn't asked to run code in 2nd DSA.

Onsite 3: System design

• Create an aggregator that allows podcasts to be registeres and users to subscribe/unsubscribe different podacasts.
• I was asked to write APIs required for it and different HTTP status code that our API can support.
• Make sure you know when to return what http status codes.
  http://en.wikipedia.org/wiki/List_of_HTTP_status_codes

Just go through all the status codes.

• Discussion included what kind of DB should be used. SQL vs NoSQL etc.

Onsite 4: System design

• Create a temp email service with TTL of 5 hours per email
• How to generate unique emails that are not too long.
  My suggestion is to use a redis counter that starts from 1 Billion and then increment it by 1 when a new email is created. The number is not a appropriate email-id so it should be base62 encoded which will convert it into alpha-numeric string. To make it more secure and unpredictable, the service can pick a random adjective from a huge list (5k english words) and append the counter string to it.
• What kind of DB to store the create the emails?
• How will access be denied once the email id expires?
• Discuss Data archival once the emails are expired.

Verdict: Reject. System design feedback was not great.

Interviewers were good and helpful.