Reader question — Batch, streaming, and the honest difference

Reader question on Batch, streaming, and the honest difference, and the answer belongs somewhere more findable than an email.

Streaming is not "batch but faster". It is a different consistency model with different failure modes, and most teams that adopt it did not need to.

The question was, roughly, "when does this stop applying?" — which is the right question and the one lessons routinely fail to answer. Every technique has a range of validity, and stating it is what separates a lesson from a recipe.

It sits in the Getting the data in module. The exercise is a thinking one rather than a query one — some of this material is about deciding what to compute, and that does not need a keyboard.

Ordering matters here more than in most courses. It follows What a pipeline is really doing and leads into Idempotency, backfills, and yesterday arriving twice, and reading it out of sequence mostly works but costs you the setup.

Free means free, and it also means we can rewrite it whenever it is wrong. No edition, no errata PDF, nothing to repurchase. The whole course is 36 lessons and the fixes land the day we find them.