AsyncAPI for Event Contracts

_Locale: en-US · Lesson: DAT-014 · Public order: 71_

Outcome and working artifact

This lesson produces a AsyncAPI Event Contract Review Record v1: a decision artifact that separates observations, assumptions, limits, and required evidence. The goal is a transferable model, not memorized tool names.

می‌تواند «AsyncAPI برای Event Contracts» را برای یک domain محدود مدل کند و constraint، compatibility یا recovery evidence لازم را مشخص کند.

Boundary model

An event payload schema is only one part of an event contract. The contract also needs the channel and address, the described application's operation and action, message identity, protocol binding assumptions, examples, and explicit limits on delivery guarantees. AsyncAPI makes these parts inspectable; it does not operate the broker or prove durability and ordering.

Keep three labels throughout the work: observed, bounded inference, and needs verification. When evidence is unavailable, record unknown. A product name or a passing happy path is not a substitute for evidence.

1. Model the channel before the payload

A message has meaning in a communication context. Record the logical channel, runtime address rule, and which application the document describes.

2. Send and receive are perspective-bound

An operation action is interpreted relative to the described application. Avoid absolute producer/consumer labels unless the system boundary is explicit.

3. Message identity matters

Name, headers, correlation information, content type, payload schema, and examples should agree. Reusing a payload shape does not automatically make two messages equivalent.

4. Bindings narrow protocol assumptions

A Kafka, AMQP, MQTT, or HTTP binding can record protocol-specific metadata. It does not prove that deployed broker configuration matches the document.

5. Reliability remains an implementation decision

Exactly-once, ordering, retention, retry, dead-letter handling, and idempotence require separate evidence. Do not infer them from a valid AsyncAPI file.

Five-step method

1. Declare the described application and its system boundary.
2. Define channel/address, message identity, headers, payload schema, and examples.
3. Add operations and interpret send/receive from that application's perspective.
4. Validate examples and deliberately break a message reference, operation action, and binding assumption.
5. Record transport and delivery properties that remain outside the document and need deployment evidence.

Worked case

The Orders service document describes channel orders.created and a receive operation because the described application consumes the message. The OrderCreated message has a correlation ID, JSON payload schema, and valid example. One mutation points the operation to PaymentCaptured; another flips the action while keeping the same application perspective. Both are caught in review. A Kafka binding note is preserved as an assumption, while retry and dead-letter policy remain explicitly outside the document proof.

Decision and evidence matrix

Failure probes and repair

• An AsyncAPI document proves exactly-once delivery, ordering or broker durability.
• A message payload schema is the complete event contract.
• The action send/receive is an absolute system-wide producer/consumer label independent of the described application.
• Protocol bindings remove the need to verify deployed broker configuration.

For each statement, narrow the claim, create a counterexample, and name the observation that could confirm or reject it.

Transfer challenge

Change the scenario so that one assumption in the worked case no longer holds. Rebuild the AsyncAPI Event Contract Review Record v1 without copying the earlier decision, then explain what changed in the input and what stayed stable in the decision rule.

What this does not prove

This lesson does not claim certification, production guarantees, or coverage of every implementation. Its conclusion is valid only within the scenario boundary, dated sources, and recorded observations.

Self-check

• [ ] Did I separate responsibilities from framework or tool names?
• [ ] Did I state at least one failure probe and its predicted observable?
• [ ] Are fact, inference, and design choice visibly separated?
• [ ] Did I record non-claims and missing evidence?
• [ ] Did I complete transfer in a changed context without a prepared answer?

Sources and freshness boundary

Sources were reviewed for the frozen Bible as of 2026-09-19. A review_due date triggers a versioned requalification; it does not authorize silent in-place edits.

• ASYNCAPI-3.1 — Current AsyncAPI 3.1.0 specification: channels, messages, operations, action semantics and bindings. (https://www.asyncapi.com/docs/reference/specification/v3.1.0; review: 2026-10-17)
• ASYNCAPI-REL-3.1 — Official 3.1.0 release note and current-version context. (https://www.asyncapi.com/blog/release-notes-3.1.0; review: 2026-10-17)