Karat Interview-

5 System Design Questions:

1. You want to create FB like social media platform with post functionality. Each user is having n friends and you need to show friends count with along with each post made by a user. How will you design/ approach on fetching the friends count with each post?
   2 Tables were provided -
   T1 having user details
   T2 having user and friends mapping
   Solution was expected for millions of users

2 You are working on Google Doc like system -

• Multiple users can work on same doc at run time
• one doc should be handled by one server only
• assume we have sufficient servers to handle the documents
  Load balancer is working in round robin mode to permanently assign server to a doc
  Q - What is the problem with the approach?

3. Eventual or Strong consistency for :

• API call with allowed latency of 30 sec, retrieving metadata for video like author, genre, view count etc.
• A analytics web page system to record every click on hot webpages
• Banking system with deposit and withdrawal system

4. We have e-sign doc system (like docusign/echosign) and we need sign of 100+ people only after that document will be marked as complete. But due to a bug some people did not recieved notifications to sign the doc and those notifications are lost.
   We have info - a) Table with records of all compelted docs b)logs from prod servers which are having details of successfully sent notifications only ( no failed ones)
   Q- Post bug fix how to identify and send notification again to the failed ones? Consider a system with tens of millions of docs

5. We have a system pipeline with multiple stages ( components) to process the documents and each component has its own processing capacity, let say we have A,B,C and having processing capacity of 10,20,50 docs then Q- What is the thoughput of system?

Coding Question -
we have a office attendance logs with us and need to find who has violated the flow : entry -> exit -> entry -> exit is the right flow and entry -> entry is the wrong flow and exit -> exit is also wrong flow
find and return the list of names with entry and exit violations

records1 = [
  ["Arjun",    "enter"],
  ["Riya",     "exit"],
  ["Arjun",    "enter"],
  ["Arjun",    "exit"],
  ["Meera",    "exit"],
  ["Kabir",    "enter"],
  ["Meera",    "enter"],
  ["Amit",     "enter"],
  ["Meera",    "exit"],
  ["Sneha",    "enter"],
  ["Kabir",    "enter"],
  ["Rahul",    "exit"],
  ["Rahul",    "enter"],
  ["Kabir",    "exit"],
  ["Meera",    "enter"],
  ["Meera",    "exit"],
  ["Sneha",    "exit"],
  ["Kabir",    "enter"],
  ["Kabir",    "enter"],
  ["Meera",    "exit"],
  ["Kabir",    "exit"],
  ["Kabir",    "exit"] 
]

Expected output: ["Amit", "Rahul", "Arjun", "Kabir"], ["Meera", "Riya", "Rahul", "Kabir"]

records2 = [
  ["Arjun", "enter"],
  ["Arjun", "exit"],
]

Expected output: [], []

records3 = [
  ["Arjun", "enter"],
  ["Arjun", "enter"],
  ["Arjun", "exit"],
  ["Arjun", "exit"],
]

Expected output: ["Arjun"], ["Arjun"]