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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.
Source, and C Source Code
Depending on what you want to do, https://github.com/tuvtran/project-based-learning that link has a large list of projects that should make it pretty apparent that you know how to program. Don't be discouraged if you find it difficult, most of those topics are difficult.
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.