A database 'unbundled' is an approach to rethinking systems by breaking out various concepts found inside a traditional database into separate layers, allowing for more control and flexibility in building independently deployable services that can share datasets without shared mutable state. This approach uses Kafka's distributed log as the core element, which provides a low-coupling mechanism for sharing data. By unbundling a materialised view into a continuously updating cache, services can have functional properties similar to traditional databases but with better scalability and predictability. The unbundled database concept is beneficial in reducing coupling between services, making it easier to release individual components without affecting others, and enabling services to take only the data they need at a point in time, resulting in smaller and more efficient views.