In DAY 04, I start with Amazon RDS and I keep it very simple: RDS is a managed relational database service on AWS. That “managed” part is the real value—because normally you’d install the database software, patch it, monitor it, handle backups, and scale storage yourself. With RDS, AWS takes care of all that, and you focus on your application and your data. I also show you the common engines you can run (like MySQL and PostgreSQL) and why features like backups and Multi-AZ matter when you move toward production setups. Then we go hands-on in the AWS console: I create an RDS instance (I use Easy Create + MySQL + Free Tier to avoid a huge form), and I show you exactly what connection details you must copy at creation time—endpoint, username, and the autogenerated password (and why you should never share it). After that, I connect a Spring Boot app to RDS using application.properties and JPA. We hit a very real issue—RDS blocks the connection because the DB isn’t publicly accessible—so I modify the instance to enable public access, connect via MySQL Workbench, create the schema, and finally let Hibernate create a table using ddl-auto=update. I end by stressing the most important AWS habit: delete/stop resources (RDS, S3, etc.) so you don’t get billed unnecessarily, and always check the region you worked in.