QuestDB

QuestDB is an open-source time-series database aimed at high-speed ingestion and fast analytical queries, with a focus on use cases such as capital markets, tick data and real-time analytics. One SQL engine covers ingestion, stream processing and long-term storage, so teams query live data and years of history the same way.

The engine is written in Java that avoids garbage collection, with C++ and Rust used on performance-critical paths. Data is held in memory-mapped, time-partitioned columns, and queries run across all CPU cores using SIMD and JIT-compiled filters. No third-party libraries sit on the data path. Data moves through three storage tiers: Apache Parquet files, native columnar partitions, and a write-ahead log that is written in parallel. In the open-source edition you convert partitions to Parquet manually, while the Enterprise edition automates tiering to object storage. Because the data stays in open formats (Parquet, Iceberg and Arrow), other tools can read it, and the README publishes benchmark figures for ingestion and query streaming.

QuestDB is Apache-2.0 licensed and runs on your own servers, with documentation also available in Chinese. It suits teams building financial, industrial or telemetry platforms who need very fast time-series ingestion.