Instagram has 1 billion monthly active users. There are very few services in the world that has that much traffic, and probably there are zero services in the world that have that many images stored.
So, what is the system architecture of Instagram? This article shows an overview of what that is, and it’s way easier than you may expect.
Overall it’s a simple Python + Django + Celery application, with a few layers of cache and multiple databases to store different information.
This shows that even if you have the scale of one of the biggest systems in the world you don’t need to use any “fancy” technology, and most of the battle-tested solutions (like Python, Django, PostgreSQL, etc.) can easily handle your scale (considering that probably your scale is multiple orders of magnitude smaller than the one of Instagram).
Next time in your startup someone mentions that you need 100s of different microservices and 10s of different databases to store your data “at scale” you can refer them to this article.