The correct answer is the strangler fig pattern, which enables incremental migration to microservices without downtime. This approach works by placing Amazon API Gateway in front of the existing monolithic application on EC2, then gradually routing specific API endpoints to new AWS Lambda functions while the monolith continues handling the remaining traffic. On the AWS Certified Solutions Architect Professional SAP-C02 exam, this pattern tests your understanding of risk-free, phased modernization strategies—a common scenario where candidates mistakenly choose a full cutover or database-first approach. The exam often presents a trap where you must recognize that the strangler fig pattern decouples migration from infrastructure changes, focusing on traffic routing rather than data refactoring initially. Remember the mnemonic: “Strangle the monolith, one endpoint at a time—route, replace, retire.”
SAP-C02 Continuous Improvement for Existing Solutions Practice Question
This SAP-C02 practice question tests your understanding of continuous improvement for existing solutions. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A company has a monolithic application running on a single EC2 instance. The application experiences performance issues during peak hours. The company decides to migrate to a microservices architecture using AWS Lambda and Amazon API Gateway. The migration must be done incrementally without downtime. What strategy should the company use?
Deploy all microservices in a new VPC and cut over DNS after testing.
Why wrong: Cutover causes downtime.
B
Create a new version of the monolith that calls Lambda functions as backend.
Why wrong: Still requires a full deploy.
C
Use AWS CodeDeploy to perform a blue/green deployment of the monolith to Lambda.
Why wrong: Monolith cannot be directly deployed to Lambda.
D
Use the strangler fig pattern: implement API Gateway to route traffic to new Lambda functions for specific endpoints while keeping the monolith for others.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use the strangler fig pattern: implement API Gateway to route traffic to new Lambda functions for specific endpoints while keeping the monolith for others.
Option B is correct because the strangler fig pattern allows incremental replacement of functionality by routing specific requests to new microservices via API Gateway while keeping the monolithic application for the rest. Option A is incorrect because full migration at once risks downtime. Option C is incorrect because pattern does not require database changes initially. Option D is incorrect because deployment pipeline is not a migration strategy.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Deploy all microservices in a new VPC and cut over DNS after testing.
Why it's wrong here
Cutover causes downtime.
✗
Create a new version of the monolith that calls Lambda functions as backend.
Why it's wrong here
Still requires a full deploy.
✗
Use AWS CodeDeploy to perform a blue/green deployment of the monolith to Lambda.
Why it's wrong here
Monolith cannot be directly deployed to Lambda.
✓
Use the strangler fig pattern: implement API Gateway to route traffic to new Lambda functions for specific endpoints while keeping the monolith for others.
Why this is correct
Allows incremental migration without downtime.
Related concept
Static NAT maps one inside address to one outside address.
Common exam traps
Common exam trap: NAT rules depend on direction and matching traffic
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Detailed technical explanation
How to think about this question
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
KKey Concepts to Remember
Static NAT maps one inside address to one outside address.
PAT allows many inside hosts to share one public address using ports.
Inside local and inside global describe the private and translated addresses.
NAT ACLs identify traffic for translation, not always security filtering.
TExam Day Tips
→Identify inside and outside interfaces first.
→Check whether the scenario needs static NAT, dynamic NAT or PAT.
→Do not confuse NAT matching ACLs with normal packet-filtering intent.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Real-world example
How this comes up in practice
A healthcare organisation deploys an application with a public-facing web tier and a private database tier. The database subnet has no public IP and only accepts connections from the web tier's security group. Questions like this test whether you can design cloud network isolation using VNets/VPCs, subnets, and security group rules.
What to study next
Got this wrong? Here's your next step.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related SAP-C02 NAT questions on configuration and troubleshooting.
Continuous Improvement for Existing Solutions — This question tests Continuous Improvement for Existing Solutions — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: Use the strangler fig pattern: implement API Gateway to route traffic to new Lambda functions for specific endpoints while keeping the monolith for others. — Option B is correct because the strangler fig pattern allows incremental replacement of functionality by routing specific requests to new microservices via API Gateway while keeping the monolithic application for the rest. Option A is incorrect because full migration at once risks downtime. Option C is incorrect because pattern does not require database changes initially. Option D is incorrect because deployment pipeline is not a migration strategy.
What should I do if I get this SAP-C02 question wrong?
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related SAP-C02 NAT questions on configuration and troubleshooting.
What is the key concept behind this question?
Static NAT maps one inside address to one outside address.
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Question Discussion
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