Wissen Technology for a backend developer role at Flipkart.(12Lpa FIXED)

"I recently had the opportunity to interview with Wissen Technology for a backend developer role at Flipkart.(12Lpa FIXED)"

The process was entirely onsite, starting with an Online Assessment (OA), followed by two Technical Rounds and a Techno-Managerial Round. Each round was eliminatory."
There were around 50-60 candidates who appeared for the interview.

Online Assessment (OA):-(Cleared) (Easy)
1. The OA had 6 easy MCQs focused on OOP, mainly interfaces and exception handling.
2. Two coding (Easy)
i) Related to on counting letters and finding the first letter with a frequency of 1.
ii)Calculating the total number of candles that can be used if K wax is left.
3.SQL(Easy)
i)One question involved finding all fields greater than a given number.

Technical Rounds (R1):-(Cleared) (Medium)
1.Find Majority Element Without Extra Space.
2.Minimum number of stations required to accommodate all trains.
--> My Approach (nlogn):- Sort Based on Arrival and Departure and count using two pointer.
--> The interviewer was not satisfied with my solution, Then I used the Line Sweep technique.
Line Sweep technique:-(Used to find overlapping lines) in o(n) time ,space(2401) one day
*** Mark Arrival index with +1 and Departure+1 index with -1
*** Calculate the Prefix Sum and find the maximum.

Technical Rounds (R2):-(Cleared) (Easy)
1.Remove duplicates from Sorted Array without using extra space and replace extra element with null.
2.Buy and sell Stock o(n).
3.SQL :- Given Student, Subject and Marks Find Max Marks optained by Student in desc order.
4.A CSV File is Given Store it Some Where so that we can Find element in o(1) and previous element also.

Technical Rounds (R3):-(? On Hold Due to my less Experience less than 1 Year :( Medium )
1.How to remove dulicate file from a folder
--> First Approch :-(Using Multithreading) Campare all the file to another with the help of threads.
--> Secound Approch :-(HashSet and Multithreading) Campare all the file to another with the help of threads and store the binary converted to string
Follow Up:- How will You Handle Collsion ?{Any Idea ?? }
2.How can we prevent a server from being taken down by an IP sending excessive requests, considering the threshold is 100 requests per second per IP?
My approach: We can create a new section in the database to store request data. If an IP exceeds 100 requests per second, we will disconnect that IP.or Kafta Rate Limiter
3.Implement a retry mechanism in Java that attempts to execute a function multiple times before failing.(Assume we are retrying a certain number of times before disconnecting).
Function is genric type Hint:- use Exception handling.

I'd love to hear from others who have experience with Arary problems. How do you approach these types of questions?