-
Alpaca-API
The Alpaca API is a developer interface for trading operations and market data reception through the Alpaca platform.
-
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.
Market data is an easier one to answer. We currently use https://alpaca.markets/ and they're pretty good, but we're also looking at https://polygon.io/ as they're the industry leader (but also 2k per month for what we require).
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.