PromHouse is a long-term remote storage with built-in clustering and downsampling for 2.x on top of ClickHouse. Or, rather, it will be someday. Feel free to like, share, retweet, star and watch it, but do not use it in production yet. Time series in Prometheus are identified by label name/value pairs, including __name__ label, which stores metric name. Hash of those pairs is called a fingerprint. PromHouse uses the same hash algorithm as Prometheus to simplify data migration. During the operation, all fingerprints and label name/value pairs a kept in memory for fast access. The new time series are written to ClickHouse for persistence. They are also periodically read from it for discovering new time series written by other ClickHouse instances. ReplacingMergeTree ensures there are no duplicates if several ClickHouses wrote the same time series at the same time.