Apache Druid

Apache Druid is an open-source analytics database designed for organizations that need to query large datasets with minimal latency. It handles both streaming and historical data, supporting OLAP queries across high-cardinality, high-dimensional datasets containing billions to trillions of rows without requiring pre-defined schemas or result caching. The system excels at high-concurrency workloads, processing hundreds to hundreds of thousands of queries per second while maintaining consistent performance. Its architecture combines in-memory data storage with columnar compression, native integration with streaming platforms like Apache Kafka and Amazon Kinesis, automatic failover and replication, and configurable tiering for balancing performance and infrastructure costs.