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InfluxDB
Power Real-Time Data Analytics at Scale. Get real-time insights from all types of time series data with InfluxDB. Ingest, query, and analyze billions of data points in real-time with unbounded cardinality.
GW2 Clarity most likely. It doesn't work in sPvP/WvW though, since those modes limit the information outside addons have access to. It also can't show every buff, because buff IDs need to be added manually by the author (although you can help their efforts on Github). Additionally, it doesn't show the duration of buffs, only whether they're applied to you or not, and the amount of stacks you have.
NOTE:
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Hence, a higher number means a more popular project.