Solving duplicate data with performant deduplication

QuestDB is an open-source time-series database designed for demanding workloads that provides ultra-low latency and high ingestion throughput, supporting Parquet and SQL to maintain data portability without vendor lock-in. The article explores the challenges of data deduplication, particularly in time-series and event data where duplicate entries can slow down processes and distort datasets. An experiment comparing QuestDB, Timescale, and Clickhouse reveals that QuestDB offers the most efficient deduplication with only an 8.3% performance degradation, supporting exactly-once semantics with minimal impact on ingestion performance. While Timescale ensures uniqueness through unique indexes, and Clickhouse accepts duplicates to later compact them, QuestDB achieves deduplication during ingestion using UPSERT Keys, ensuring no duplicates in query results. The native deduplication feature, introduced in QuestDB 7.3, offers strong performance while guaranteeing exactly-once semantics, making it a robust choice for applications needing reliable and efficient data handling.