The problem I’m having is that I have a 3rd party consultant who will be building a data warehouse for me. However I am not sure what level of environment access they would need from my transactional business systems for ingestion, ETL and data mart creation. One option would be to mask any sensitive PII production data and give them. However I am unsure if they would need unmasked data for the nature of the work, which is essentially to build the warehouse system. They will have to do a few business intelligence reports also once the warehouse is built. From your experiences, what level of access is required by data engineers , data modellers and report developers when building a new data warehouse?