QuestDB is an open source database for time series, events, and analytical workloads with a primary focus on performance. https://github.com/questdb/questdb
Swetrix brings an advanced and customisable analytics service for your web applications. We are fully opensource, support lots of features and selfhosted variants. No cookie banners needed. Track every metric you need without invading your users' privacy.
Warp 10 is a platform designed to collect, store, and analyze time series and geolocated data. It is both a time series database and an associated analytics environment. Its data processing language called WarpScript offers over 1200 functions.