SAP-C03 practice question: Replatforming, refactoring and modernization (strangler fig)
Resilience, Migration, and Business Continuity A free question from our original SAP-C03 practice exam. Try it, then open the answer to see why each option is right or wrong.
A retailer's order-management application is a monolith on servers in its data center. Its web front end calls the monolith's order, returns and gift-card paths, and each path has a different owner and release schedule.
The retailer wants to move each path to a new microservice on containers, one path at a time, while the monolith keeps serving the paths not yet moved. Customers must see one consistent API throughout, and a path must be switched back quickly if the new service misbehaves.
Which approach meets these requirements?
Choose one answer.
AA. Rewrite the whole monolith as microservices on containers, and switch all customers to the new system in one planned cutover after the testing is complete.
BB. Lift the monolith as it is onto Amazon EC2 instances in AWS, and keep the code unchanged until the whole application can be rewritten later in a single project.
CC. Put an Application Load Balancer or API Gateway in front of both systems, route each path to its new microservice when it is ready, and switch a path back by changing its route.
DD. Send every request to both the monolith and the new microservices, and have the front end compare the two responses, so that each new service is proven before any customer traffic moves to it.
Show the answer and explanation
Answer: C
A. Wrong: A single cutover of a full rewrite gives no staged path and no quick way to return one path to the monolith. It also puts every path at risk on the same day.
B. Wrong: A lift-and-shift keeps the monolith as one unit, so the paths cannot move independently to containers. The option is a rehost, not the staged modernization the retailer wants.
C. Right: Correct. This strangler fig pattern moves one path at a time behind a single API, and reverting a path is a routing change. Customers see one consistent endpoint throughout.
D. Wrong: Duplicate writes to both systems can record each order twice or diverge the data, and the comparison does not switch any path over. The approach does not provide a clean staged move.
Explanation
A routing layer in front of both systems moves one path at a time and lets the team switch a path back by changing its route, which matches the strangler fig pattern. A full rewrite cutover, a lift-and-shift and dual writes each fail the staged move or the rollback requirement.
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