TimescaleDB 2.9 introduces hierarchical continuous aggregates, a feature that allows for more efficient data storage and faster query performance by building one continuous aggregate on top of another. This functionality addresses the challenge of managing large volumes of time-series data, typically collected at high granularity levels and later downsampled for practical use, such as in dashboards. Users can now roll up aggregated data from, for example, five-minute intervals to 15-minute intervals, reducing the need to retain raw data and thus decreasing storage requirements. This approach not only optimizes storage but also accelerates query processing, as calculations are performed on fewer data points. The new feature extends TimescaleDB's capabilities, allowing for complex branching of aggregates and enabling users to implement diverse retention policies. TimescaleDB 2.9 also brings additional enhancements like time zone support for time_bucket_gapfill and fixed scheduling for background jobs, aiming to enhance user experience and functionality.