Falck Interview Question

What can we do to optimise a slow running SQL job? How do you remove duplicates from a query using window functions? What is a dataframe? Do you know Kimball? Why use a surrogate key? What are some types of indexes? What is a pull request? How to flatten an arraw of Jsons with specific method in mind? Why normalisation vs denormalization? Why use a Snowflake schema instead of star schema?