Amazon Business Intelligence Engineer I interview questions

1st) No Phone screening round, a ETL assignment was sent to me which included task of migration of csv to Redshift with the help of COPY command. Basic data cleaning and missing value imputation in Pandas , SQL for Redshift where I had to create table, data insertion in Redshift (COPY command to migrate clean csv to Redshift assuming csv is in S3), Dropping duplicates (I used CTE with ROW_NUMbER() ) for this. This round was cleared and feedback was positive) 2) Phone screening - With HR on behavioral questions. (Cleared this round) 3) Hiring manager - Going through CV, mostly asking about ETL incremental pipelines where I reduced the warehouse cost by 50% . The manager seemed to doubt my resolution and also asked a behavioral Question to which I answered that I'm afraid that I couldn't answer as such incident didn't took place yet to justify any situation. He was still enforcing me to think again. NOTE : HR told me generally Task / Assessment round happens after hiring manager round but it was sent to me first before even phone screening round - Which made my overall experience with interview process negative because I spent a week time on optimizing the ETL solution, documenting the report and approach that I took. If this could had been given to me after hiring manager round it could had been better.