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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 recommend https://github.com/nlohmann/json . I don't think it gets easier than that:
this what I saw at first https://github.com/protocolbuffers/protobuf
About on par with nlohmann is a binary serialization lib called Bitsery. It's easy to use, and will be a lot more performant than json. The downside is that the serialized data won't be human readable.
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