Goldman Interview experience | Associate

Okay lemme dot it down clearly here so that it helps :
YOE : 2 years 6 months
CoderPad :
1 medium - related to BFS , finding the shortest distance between train stations.
2 easy - finding average of class marks.

Superday :
There were two interviewers for each round

1st Round -
They started off with the question - generating all possible words in the dictionary with given alphabets (using a Trie and Hashmap.) .They asked me to implement a Trie with insert and search functionality. As I saw this question for the first time , I took around 30-40 mins to solve this and pass their test cases.
Secondly, they gave an easy question (Valid Parentheses Check) , I solved it under 15 mins , they did dry run my code with 3-4 examples and were satisfied.

2nd Round -
This was all about resume , Java Concepts and DSA concepts ( Hashmap internal working and also asked me to implement a Hashmap class in Java )
Some questions on Java that I remember :

1. Multithreading , how to generate a thread.
2. Difference between start and run.
3. Difference between runnable and thread class
4. Then they jumped on Collections, with difference in Comparator and Comparable, asked me to implement sorting a class according to name , lexicographically.
5. Asked me about hashcode and equals method and their uses
6. I did mention making a custom logger in my resume , so they drilled me on design patterns (singleton, builder, factory, abstract factory)
7. Then they asked my to implement an immutable class , I did that.
8. Asked me about Refactoring in hashmap, tri-fi threshold.
9. They insisted on Java 8 and 7 features , I told them about all the new Java features introduced, including method referencing and stuff.
10. They were satisfied by this point (lmao) but they did ask a last question regarding my project and rxJava because of my resume , which i answered.

3rd Round -
This was a System design round
1st interviewer gave a fairly easy system to design where I had to deal with events based on priority and make transactions to DB .I knew he was hinting towards Kafka so I mentioned it. Then he asked about internal structure and working of Kafka , which I knew so I answered clearly, he was satisfied .
Then there was the tech lead , who asked me to implement snake and ladders game , but the twist here was, he also wanted me to write the logic of the game, which I did.
Interviewers were helpful throughout, this round was fun and it was very interesting solving out the logic part.

4th round -
HM round, basic resume questions and team introduction.