QuestDB

QuestDB is an open-source, high-performance time-series database engineered for demanding workloads, from trading floors to mission control. Built with Java and C++, it delivers ultra-low latency (under 10ms query response), high ingestion throughput (16 million+ rows per second via InfluxDB line protocol, 8 million rows per second via PGWire), and a multi-tier storage engine combining WAL (Write-Ahead Log) hot storage with cold Parquet tier for cost-effective long-term retention. QuestDB uses SQL as its primary query language, eliminating the need to learn a custom query DSL, with native time-series extensions including ASOF JOIN (aligning time-series from different sources), SAMPLE BY (downsampling with 12 aggregation functions including first, last, min, max, avg, count, sum, ksum, jsum, median, stddev), LATEST ON (finding most recent values per key), and time-bucketed analytics. The database supports PGWire (PostgreSQL wire protocol) for compatibility with existing PostgreSQL drivers, REST API, and native clients for Java, C/C++, Go, Python, Rust, Node.js, and .NET. As of 2026, QuestDB version 8.x has over 17,100 stars and 170+ contributors, licensed under Apache 2.0. Customers include Airbus (billions of data points per day), B3 Exchange (99.9% uptime for CSD tick data), One Trading (regulated 24/7 futures exchange), BTG Pactual, HDFC Bank, Mizuho, OKX, and Ripple.