SDE - 2

Given a string input of length n, find the length of the longest substring without repeating characters i.e return a substring that does not have any repeating characters.

Substring is the continuous sub-part of the string formed by removing zero or more characters from both ends.

You are given a string 's' that represents a Roman number. Convert the Roman number to an integer and return it.

Roman numerals are represented by seven different symbols: I, V, X, L, C, D, and M.

Table of values:

Symbol       Value
I             1
V             5
X             10
L             50
C             100
D             500
M             1000

For example:

3 is written as III in Roman numeral, just three ones added together. 13 is written as XIII, which is simply X + III. The number 25 is written as XXV, which is XX + V 

In designing a payment system, I focused on ensuring robust failure handling and clear transaction states, including pending and completed. The system is designed to flag payment providers for the first 60 minutes in case of downtime, allowing for swift recovery actions. If the provider remains unresponsive beyond this period, we take responsibility for blocking payments. Additionally, the system incorporates a mechanism for processing refunds efficiently, ensuring that customers receive their money back promptly if needed. This architecture prioritizes reliability and user trust, essential for a seamless payment experience in a dynamic environment. It was a high-level discussion with no coding round.

In the interview, I was tasked with designing a team creation service for Dream11, focusing on both functional and non-functional requirements. The service needed to allow users to create teams of up to 11 players, enforcing constraints on player types and preventing modifications once a contest started, to ensure fairness.

For the non-functional requirements, the system required high scalability to handle many concurrent users, low-latency data retrieval, and robust error handling. I proposed using Aerospike for its high-performance capabilities and MongoDB for its flexibility in managing unstructured data.

However, I struggled to articulate the rationale behind my choices. When asked about Aerospike, I realized I needed a deeper understanding of its internal workings. Similarly, I couldn't convincingly justify selecting MongoDB over relational databases like PostgreSQL. This experience highlighted the importance of understanding the "why" behind technology selections, which ultimately affected my performance in the interview.