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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.
For special symbols, there was actually a dedicated web app; I can't find it atm though a quick search yields results such as typing.io. You can also import such text into an universal typing-practice application such as Amphetype.
NOTE:
The number of mentions on this list indicates mentions on common posts plus user suggested alternatives.
Hence, a higher number means a more popular project.