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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.
I've had some success with em-websocket. I haven't specifically tried integrating it into a Sinatra app, but I was able to make it provide a websocket interface to an existing TCP server in an afternoon.
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