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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.
There's an android developer roadmap that you can find here. Also, developing small and simple projects at least every week would benefit you, as opposed to charging D'Day style into every technical concept, architecture and essential library.
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.