Lambda versions, aliases, and canary traffic

Exam alignment: DOP-C02 Domain 1 task statements for pipelines, testing, artifacts, or deployment.

Learning objective

Publish immutable versions and progressively route traffic through a stable alias.

Difficulty / Schwierigkeitsgrad	Intermediate
Study time / Lernzeit	120 minutes
Prerequisites / Voraussetzungen	Previous lessons in this volume

Professional scenario

The team updates $LATEST directly for a high-volume function.

Core concepts

• Published versions are immutable snapshots.
• $LATEST is mutable.
• Aliases provide stable qualified names and weighted routing.
• Version-specific telemetry is required during canary rollout.

Architecture flow

1. Identify the release input and immutable identity.
2. Select the managed AWS control plane and least-privilege role.
3. Execute build, test, artifact, or deployment work.
4. Collect service events, logs, reports, and runtime metrics.
5. Stop, retry, or roll back according to explicit rules.

Decision matrix

Requirement	Preferred choice	Reason
Stable caller target	Alias	Caller ARN stays stable
Lowest initial risk	Canary or linear	Limits exposure
Exact rollback	Move alias to old version	Fast traffic recovery

Failure modes and troubleshooting

• Clients call $LATEST.
• Metrics combine old and new versions.
• Async retries create duplicate processing.

Security and operations

• Use short-lived service roles and least privilege.
• Encrypt artifacts and protect logs from secret exposure.
• Record changes and approvals for audit.

Hands-on lab

Goal / Ziel: Publish two versions and route a small weighted share.

Tasks

1. Create the smallest safe test architecture.
2. Implement or simulate the main workflow.
3. Introduce one controlled failure.
4. Diagnose it from service evidence.
5. Document cleanup and one improvement.

Validation

• The workflow uses an immutable version.
• A required failure blocks promotion.
• The diagnosis identifies the first failed transition.

Cost control / Kostenkontrolle: Keep resources short lived; read cleanup before starting.

Cleanup

1. Delete pipeline/build/deployment resources.
2. Delete temporary artifacts, images, logs, and roles.

Exam traps

• Treating $LATEST as immutable.
• Ignoring idempotency.

Key takeaways

• Published versions are immutable snapshots.
• Version-specific telemetry is required during canary rollout.
• Decisions must be justified by requirements and failure behavior.

Review questions

1. What is the immutable release identity?
2. Which evidence proves failure or success?
3. What is the safest recovery action?

Answers

1. A version, digest, or uniquely versioned artifact.
2. Service events, logs, reports, health checks, and runtime metrics.
3. Restore the known-good version using the configured rollback path.