TimescaleDB is an open-source time-series database that leverages PostgreSQL and extends it to scale for time-series workloads. It partitions data into chunks, allowing for faster inserts and optimizing query performance by intelligently reducing the number of chunks queried. TimescaleDB optimizes query performance using three stages: planner exclusion (preventing unneeded chunks from entering the query plan), executor startup exclusion (removing unneeded chunks before execution), and executor runtime exclusion (preventing unneeded chunks from being accessed during execution). These optimizations result in significant performance improvements, particularly for queries with constraints on partitioning columns. By leveraging PostgreSQL's internals and implementing custom scan nodes, TimescaleDB achieves constraint exclusion at plan time, executor startup, and runtime, making it a powerful tool for time-series data analysis.