FDE Foundations · Module 5: Data & Integration
Batch vs Events: Choosing
Batch and events answer different questions: batch answers 'what is the state', events answer 'what just happened'. Choose per use case and be able to defend it.
9 min reading
Objectives
- Compare batch and event architectures on five axes
- Choose per use case, not per fashion
- Explain the choice to the customer in their terms
Five axes
| Axis | Batch | Events |
|---|---|---|
| Latency | Minutes to hours | Seconds |
| Complexity | Lower (a job plus a schedule) | Higher (queue, workers, dedup) |
| Cost at volume | Predictable, cheap | Scales with event count |
| Failure model | Rerun the job | Replay the stream |
| Fit | Reporting, reconciliation, backfills | Operational triggers, UIs, alerts |
Choose per use case
A nightly margin report is batch; a fraud hold on a card payment is an event. Most field engagements need both, and the honest architecture says so: events where latency has business value, batch everywhere else. Do not build streaming infrastructure because it impresses; every moving part is something the customer must operate after you leave.
Defend it in customer terms
Translate the choice: "Invoices settle nightly, so batch at 2 a.m. keeps costs low and failures simple to rerun. Payment holds need a decision in seconds, so those flow as events with a replayable queue." That sentence, with the failure story for each side, is what the customer's architects need to hear.
When in doubt, start batch and add events for the specific paths where seconds matter. Removing events later is harder than adding them late.
Quick check
An optional 2-3 question self-check. Answers never leave your device, are not stored, and never count toward any assessment.
Exercise
Pick the architecture for four fictional use cases (nightly inventory report, out-of-stock alert, month-end reconciliation, live order tracking), with a one-line defense for each.
Pass criteria
Each use case has a choice and a one-line reason referencing latency or failure model; at least one case mixes both correctly.