Databases and Streams

Change Data Capture (CDC): Turning a database into a stream. We can hook into the database's replication log and stream all changes to other systems (search index, cache, data warehouse). This decouples the systems.

Event Sourcing: Instead of storing the current state, store the sequence of events that led to that state.

• "Student cancelled course" (Event) vs "Delete row from table" (Side effect).
• Allows reconstructing state at any point in time.
• Easier to debug and audit.