Jeff’s Note #
Unlike generic exam dumps, ADH analyzes this scenario through the lens of a Real-World Lead Developer.
For DVA-C02 candidates, the confusion often lies in how to execute gradual deployment strategies for Lambda functions invoked via the SDK. In production, this is about knowing exactly how Lambda versioning and aliases work with traffic weights to control invocation percentages smoothly. Let’s drill down.
The Certification Drill (Simulated Question) #
Scenario #
TechBuzz is building a real-time collaboration tool. A backend developer is updating an AWS Lambda function that logs user activity to a DynamoDB table. A web app server invokes this Lambda function using the AWS SDK. After thorough testing, the developer wants to deploy the new Lambda function code but only wants a small percentage of the AWS SDK invocations to use the updated code while the rest continue using the existing version.
The Requirement: #
How should the developer implement this gradual rollout so that only a controlled percentage of SDK calls invoke the updated Lambda function code?
The Options #
- A) Configure a Lambda function version with a specific weight value assigned to the updated code.
- B) Create an alias for the Lambda function and configure a weighted routing policy between the original and updated versions.
- C) Create an Application Load Balancer and specify weighted target groups pointing to the original and updated Lambda functions.
- D) Create a Network Load Balancer and specify weighted target groups pointing to the original and updated Lambda functions.
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Correct Answer #
B
Quick Insight: The Developer Imperative #
For the DVA-C02 exam, understanding Lambda deployment best-practices is critical: Lambda aliases enable controlled traffic shifting without requiring changes to the SDK invocation code. The traffic weight set on aliases allows you to test new versions with a small portion of invocations, which aligns perfectly with the requirement here.
Content Locked: The Expert Analysis #
You’ve identified the answer. But do you know the implementation details that separate a Junior from a Senior?
The Expert’s Analysis #
Correct Answer #
Option B
The Winning Logic #
This approach leverages Lambda aliases with weighted traffic shifting, which is the native and most supported method for gradual deployment in Lambda invoked via the SDK.
- An alias is a pointer with a name (e.g., “prod”) that can route a percentage of invocations to one version and the rest to another.
- The AWS SDK calls the Lambda function via the alias name, keeping invocation code unchanged.
- Traffic weights on the alias can be adjusted dynamically for canary or blue/green deployments, perfectly meeting the gradual rollout need.
The Trap (Distractor Analysis): #
-
Option A: Versions alone are immutable snapshots. While versions exist, you cannot assign traffic weights directly to versions without aliases. Calls to versions require specifying the version explicitly, which differs from standard SDK invocation patterns and is less practical for gradual rollout.
-
Options C & D: Application Load Balancers and Network Load Balancers do support Lambda integration, but are primarily for HTTP(s) invocation patterns and cannot perform weighted traffic shifting natively across Lambda versions. This adds unnecessary complexity and diverges from common best practices.
The Technical Blueprint #
Code Snippet - Creating Alias with Weighted Traffic (AWS CLI example) #
# Publish a new version of the Lambda function
aws lambda publish-version --function-name UserActivityLogger
# Create or update alias with weighted routing (e.g., 10% to new version)
aws lambda update-alias \
--function-name UserActivityLogger \
--name prod \
--routing-config '{"AdditionalVersionWeights": {"2": 0.1}}' \
--function-version 1
The Comparative Analysis #
| Option | API Complexity | Performance Impact | Use Case |
|---|---|---|---|
| A | Low — only versions | Inflexible rollout | No gradual traffic control via SDK calls |
| B | Moderate — alias + weights | Dynamically adjustable, minimal impact | Best for controlled gradual deployments |
| C | High — ALB setup | Latency overhead | Suitable for HTTP workloads, not SDK invocations |
| D | High — NLB setup | Latency overhead | Similar to ALB, not ideal for progressive Lambda rollouts |
Real-World Application (Practitioner Insight) #
Exam Rule #
For the exam, always pick Lambda alias weighted routing when you see “small percentage” gradual rollout or canary deployment for Lambda invoked by SDK.
Real World #
In production, advanced deployment automation may integrate CodeDeploy with Lambda for traffic shifting, but alias weights remain the fundamental mechanism under the hood.
(CTA) Stop Guessing, Start Mastering #
Disclaimer
This is a study note based on simulated scenarios for the AWS DVA-C02 exam.