Amazon Lab126 SDE 2 (ML) Interview Experience [No offer]

Current Role: Software Engineer with Computer Vision, ML, Deep learning Background, Working for a startup in Bay Area with 1.5 yrs of experience.

First round:
OO Design Question: Design email client

Second round:
Discussion about my work, at current company

Coding: Given an Array of numbers & a target value, return indexes of two numbers such that their Absolute difference is equal to target
Tip: check if num[i]+target, num[i]-target in hash

Third round:
Lunch: About my work at current company

Forth round: (Bar raiser)
LP Question: How do you deal with good quality when delivering to costumer

ML Question: How do to find thresholds for classifier? Ans: plot ROC curve
Coding: Given two dates D1 & D2. count number of days, month?

Fifth round:
Discussion about my work at current company,

Why are you leaving current job?
How to handle conflicts with team member?

Sixth Round:
Discussion about my work

Coding: find 1st missing postive number (must do in O(1) memory & O(n) time)
https://leetcode.com/problems/first-missing-positive/

I screwed first and last rounds, I didn't expect OO design question. There are two interviewers in last round Senior engineer and probably a new grad, 2nd person lead the round. I did the coding question before, but I couldn't recall optimal method.

I did nearly 150 leetcode problems, focused on top interview questions. I felt, I should start revising the problems.

Do I need to solve more questions? can any one please give me suggestions ?

I am also looking for referrals at big tech companies & startups. can any one please refer me ?

First Missing Positive - LeetCode Leetcode