An event receipt saved separately from a local mutation leaves a crash window. A unique event-ID receipt and the mutation can commit together; a replay can then skip a committed receipt.
Select the image to inspect native SVG text at full size. Light SVG · Dark SVGAssumptions and accessible description
Use a database-enforced unique event key; concurrent deliveries cannot both insert it.
Rollback both the receipt and mutation if the transaction fails. A committed receipt, not an in-memory flag, gates replays.
Distinct event IDs can represent the same business action. Define additional business keys when needed.
This does not make email, remote API calls or every downstream effect exactly once.
Alt description: Failure: event, mutation, crash before receipt, repeated mutation. Alternative: verify event, begin transaction, unique receipt with local mutation, commit and skip repeats.
Returning success before a durable handoff can lose work if the process crashes. Keep reception short, acknowledge only after accepted storage, and let a separate worker retry the retained item.
Select the image to inspect native SVG text at full size. Light SVG · Dark SVGAssumptions and accessible description
Use a durable queue or database, not a promise, process memory or an uncommitted write.
Provider timeouts and retry windows must be checked. An uncertain enqueue result can yield duplicates.
The worker needs its own deduplication, retry limits, failure visibility and side-effect policy.
Persist only approved payload data with suitable retention; this drawing is not a security checklist.
Alt description: Failure: verify event, acknowledge, lose in-memory work in a crash. Alternative: verify, durably store work, acknowledge acceptance and retry from storage.
A quoted CSV field can include a line break. The included tiny fixture has three physical lines but only a header and one data record. A line-based split is not a CSV parser.
Select the image to inspect native SVG text at full size. Light SVG · Dark SVGAssumptions and accessible description
Fixture bytes use CRLF, comma delimiter and double-quote enclosure. No trailing record newline is added.
Header is a parsed record but not a data row: two records here, one data row.
Other CSV dialects and encoding policies need explicit decisions; RFC 4180 is informational guidance.
Parsing does not certify business validity, safe spreadsheet execution or migration correctness.
Alt description: Failure: split a quoted CRLF into two rows and report a false mismatch. Alternative: choose dialect, parse quoting, retain the embedded break and validate actual records.
Technical reference: RFC 4180. Original artwork; no affiliation.
