Re: Relationship between PostgreSQL and Datalakes and etc on Azure

I'm not clear what tech in Azure tech you're referring to -- there are various MS SQL solutions out there, and then there are PowerBI type solutions.

From my perspective, PowerBI offers a lot of high level tooling that makes data warehouse/analysis type projects really fast/efficient. For analytics problems, PowerBI can be a very cost effective overall solution that is worth considering. That said, I don't think you have to give up on Postgres to get PowerBI working: https://docs.microsoft.com/en-us/power-query/connectors/postgresql

Regarding the broader "what datalake technology should I use" question -- there will never be a universal right answer, but you are writing to a Postgres sql language group. The answer for me personally is "Start by using Postgres, until you can prove that another option will be measurably better." I've been let down many times by other technologies, and Postgres just keeps working. I'm actually right now in the process of ripping out a Sparql/Neptune database solution and replacing it with Postgres. So it turns out that even for many complex graph queries, I can model the data in Postgres and get results that are far more performant (2x-4x) than dedicated graph databases.

So my personal database architecture rule now is: "Default to Postgres, and optimize with other solutions only when I find something that Postgres demonstrably can't handle." 

Good luck,

Steve