The following are the situations when you should consider using Flowables. Remember, Flowables are slower than Observables:

• Flowables and backpressure are meant to help deal with larger amounts of data. So, use flowable if your source may emit 10,000+ items. Especially when the source is asynchronous so that the consumer chain may ask the producer to limit/regulate emissions when required.
• If you are reading from/parsing a file or database.
• When you want to emit from network IO operations/Streaming APIs that support blocking while returning results, which is how many IO sources work.