Stream Data Processing Approaches

There are different approaches which stream processing applications take to handle reprocessing of messages. Depending on the requirements of solution an architect / developer can choose between one of the below

At least once:

• Each message is guaranteed to be processed
• Message may get processed more than once
• This guarantees no data loss, but does result in duplicate records passing through the system.

At most once:

• Each message may or may not be processed
• If a message is processed, it’s only processed once.
• This mostly leads to a missing data issues.

Exactly once:

• Each message is guaranteed to be processed once and only once
• An example: Credit card transactions processing, in this case if we process a message multiple times it means we’re paying multiple times, and if we drop a message means we’re not processing a payment.