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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.
As has been said it's a notification overflow indicator. You can use apps like Notification Log, which logs app notifications, and Super Status Bar/SystemUI Tuner (see documentation), which allow toggling system notifications, to help determine what notifications are causing it. App notifications usually appear on the left side of the statusbar whereas system notifications usually appear on the right. The overflow indicator may pop up both places.
NOTE:
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