Google Cloud's wide-column NoSQL database for massive volumes with millisecond latency. It is designed for millions of reads and writes per second with row-key access, not for SQL queries with joins.
In CDL it is the answer for IoT, time series, high-frequency financial data, and large-scale personalization. Question: millions of devices sending metrics every second → Bigtable. For SQL analytics on that data → BigQuery.
Cloud Bigtable is a concept that can show up on the exam. Check the full guide to see it in context.