Cutting a lesson down — Batch, streaming, and the honest difference

A note from writing Batch, streaming, and the honest difference, which took three passes to get to something short.

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 hard part of writing this was cutting it. The first version covered every case; the useful version covers the case you hit on a Tuesday and names the rest in a sentence. Completeness is a property of reference material, not of teaching material, and confusing the two produces something nobody finishes.

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.