- MySQL – Get Started
Start here. What MySQL is and where it fits against Postgres and SQLite, why 8.4 is the version to learn and what LTS means for it, InnoDB and why the storage engine is a choice you no longer have to make, the pizza-ordering database every query in this track runs against, and the full lesson index in reading order.
- AWS – Stop an RDS Instance on a Schedule with Lambda
Stopping RDS saves the instance hours but not the storage, and it does not last: AWS restarts any instance that has been stopped for seven days. That single fact is why a stop-on-a-schedule Lambda is a schedule and not a one-off click. The handler, the seven-day trap and how to notice it, and the difference between stopping an instance and stopping an Aurora cluster.
- Designing a Unique ID Generator
Four ways to mint an id at scale and the single tradeoff that decides between them: sortability against coordination. Database auto-increment, UUIDv4 and v7, a ticket server, and Snowflake — with the bit layout worked through, the clock-skew failure everyone forgets, and why a system can want two ids for the same row rather than one.
- AWS – Start an RDS Instance on a Schedule with Lambda
Starting a stopped RDS instance is one API call and a wait measured in minutes, not seconds, which changes how you schedule it. The handler, the IAM policy, and the state check that stops a retry storm — calling start on an instance that is already starting is an error, not a no-op. Plus the configuration that cannot be stopped at all: anything with a read replica, or that is one.
- Oracle Database – With Spring Boot
Driver, URL, and the colon-versus-slash that decides between a SID and a service name. A tuned Hikari and JPA configuration, a Lombok entity that does not break hashCode, the allocationSize mismatch that causes ORA-00001 under load, batching, calling PL/SQL packages, Testcontainers against real Oracle, and a table of the errors you will hit.