Jeff’s Note #
Unlike generic exam dumps, ADH analyzes this scenario through the lens of a Real-World Lead Developer.
For AWS DVA-C02 candidates, the confusion often lies in how to safely deploy API Gateway changes without impacting live production traffic. In production, this is about knowing exactly how to leverage API Gateway’s built-in traffic shifting via canary deployments to minimize errors and reduce blast radius. Let’s drill down.
The Certification Drill (Simulated Question) #
Scenario #
TechNova Solutions is building a serverless weather data service that exposes REST APIs fronted by Amazon API Gateway integrated with AWS Lambda functions. The backend stores user preference data in DynamoDB tables. TechNova manages three environments: dev, staging, and prod, each with its own separate DynamoDB table. Recently, when promoting API and Lambda code changes from staging to prod, users have reported intermittent failures. A lead developer at TechNova needs to deploy the next production update so that 20% of production API traffic goes to the new deployment while the remaining 80% continues hitting the existing, stable production version. The goal is to minimize errors any single user might face during this transition.
The Requirement: #
Implement a strategy to route a controlled 20% of live API traffic to the new production version while ensuring most users continue to use the stable API version. The deployment approach must minimize user impact.
The Options #
- A) Update 20% of the Lambda function code in the production stage and deploy. Monitor results and repeat this incremental deployment five times until all changes are live.
- B) Modify the Route 53 DNS record for the production API to use a weighted routing policy with 80% weight for the current API and 20% for the staging API endpoint.
- C) Deploy an Application Load Balancer (ALB) in front of the APIs. Change the production DNS record to point to the ALB and register the production and staging APIs as targets with weights 80% and 20%, respectively.
- D) Configure API Gateway canary deployment settings for the production stage. Set the canary traffic percentage to 20%, deploy the new changes to production, and monitor.
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Correct Answer #
D.
Quick Insight: The Developer Imperative #
- AWS API Gateway provides native canary deployments that allow fractional traffic shifts inside the same stage. This avoids DNS TTL problems and minimizes user-side caching issues.
- Unlike Route 53 weighted routing or ALB solutions, canary deployments manage traffic routing at the API Gateway layer, reducing error impact and simplifying rollbacks.
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 D
The Winning Logic #
Configuring canary deployments within API Gateway allows precise control of traffic shifting between the stable production deployment and the new update. Setting canary traffic to 20% means API Gateway itself routes 20% of incoming requests to the new Lambda-integrated deployment, while the other 80% hits the existing one. This method reduces cache inconsistency issues and DNS propagation delays that occur with weighted DNS. It also optimizes for quick rollback if errors spike in the canary version, as traffic can be instantly reverted without DNS or ALB reconfiguration.
The Trap (Distractor Analysis): #
- Why not A? Incremental manual Lambda code updates require multiple deployments and are error-prone. There is no automated traffic shifting and monitoring — this increases user exposure to buggy versions.
- Why not B? Weighted DNS routing via Route 53 does not handle API Gateway stage granularity, and DNS caching can cause inconsistent routing, exposing users unpredictably to different API versions.
- Why not C? Placing an ALB in front of API Gateway REST APIs is unnecessary and highly complex because ALB is designed for HTTP/HTTPS traffic to containers or EC2 instances, not for serverless API Gateway stages.
The Technical Blueprint #
# Example AWS CLI to deploy canary settings on an API Gateway stage
aws apigateway update-stage \
--rest-api-id a1b2c3d4 \
--stage-name prod \
--patch-operations op='replace',path='/canarySettings/percentTraffic',value='0.2' \
op='replace',path='/canarySettings/deploymentId',value='new-deployment-id'
The Comparative Analysis #
| Option | API Complexity | Performance Impact | Use Case |
|---|---|---|---|
| A | Low (manual steps) | High risk of errors | Poor for safe production rollout |
| B | Moderate (DNS setup) | High latency in update | Best for multi-region routing |
| C | High (ALB + API GW) | Overhead + complex | Not recommended for serverless |
| D | Built-in API Gateway | Low latency, safe | Ideal for staged canary releases |
Real-World Application (Practitioner Insight) #
Exam Rule #
For the exam, always pick API Gateway Canary Deployments when you see fractional traffic shifting with REST APIs backed by Lambda.
Real World #
In production, teams might combine Canary deployments with CloudWatch alarms and AWS X-Ray tracing to monitor new deployments’ health before a full rollout — automating rollback if error thresholds exceed limits.
(CTA) Stop Guessing, Start Mastering #
Disclaimer
This is a study note based on simulated scenarios for the AWS DVA-C02 exam.