Streams as a Data Source

A company runs 3,600 vending machines, and every machine sends each sale and each restock to one stream, about 64,800 records a day. Three jobs read that stream: a stock report, a refill planner for the delivery trucks, and a revenue table. Each job depends on properties of the stream, so the team has to know which ones the stream guarantees and which ones each job must provide itself.

The stream guarantees three things:

• Order within a partition. Records with the same key are stored together and read in the order they were written.
• **Retention