How Data Flows Through your Apps

On this episode of That’s Girl Code, Ellen breaks down how data actually moves through modern applications, from the moment you tap your screen to the systems that learn from that behavior and quietly reshape what you see next. Using Instagram as a running example, she walks through the full data ecosystem of an app, explaining why different types of databases exist, how OLTP and OLAP systems serve completely different purposes, and how events turn user behavior into data. The episode covers relational databases, NoSQL, object storage, graph and vector databases, and how analytics platforms like Databricks power insights, models, and decisions behind the scenes. This episode is a practical, systems-level look at how frontend, backend, and data architecture work together — and why understanding data flow is essential for building scalable, high-performing applications.