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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.
Async is only useful when you have hundreds of connections open at the same time and idling most of the time; otherwise it's a liability. If your web API does not allow that (e.g. it has rate-limiting, which most APIs do), I suggest going with a client that performs blocking I/O and spawning threads if you need parallelism. https://github.com/algesten/ureq should fit the bill.
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