[DarkContinent]

> Batch is just a special case of streaming

No. Designing a system that is always up and running and can process small amounts of data constantly is a completely different problem from designing a system that runs occasionally with a lot of data. For one thing, your output formats are usually different in the latter case (maybe you're creating a PDF for example). Also the high availability requirement just makes things different at the design level.

Finally, the author claims it's not hard to switch between batch and streaming. With a large volume of preexisting data, this is just not true. For example, if you make a REST API call for each document in a DB, it can take days or months to load that. If batching together documents isn't a possibility, how do you move data between stores easily? (This data movement is often required when switching between batch and streaming.)

[lkdfjlkdfjlg]

I'm seconding this, and I have first hand experience in exactly this problem, in finance. My first boss also had the view that "batching is a special case of streaming where you stream N and streaming is also a special case of batching where the batch size is 1 and so it doesn't matter which one you implement". This was never performant enough and he was eventually asked to leave.

[erik_seaberg]

The key is working incrementally, not sitting idle for months and then hammering production as hard as possible trying to get all the deferred work done in exactly one batch.