Migrating a Legacy Application with No Code Changes Using Rehost Strategy
A company is migrating a critical application to AWS using the 7 Rs migration strategy. The application is tightly coupled with legacy infrastructure and has compliance requirements that prevent any code changes. The migration must be completed in 3 months. Which strategy is most appropriate?
Quick Answer
The answer is the rehost strategy, also known as lift-and-shift, using AWS Application Migration Service (MGN) and Amazon EC2. This is correct because the 7 Rs migration strategy’s rehost option is explicitly designed for scenarios requiring no code changes, as it moves the application as-is to the cloud while preserving its existing architecture and dependencies. For the AWS Certified Solutions Architect Professional SAP-C02 exam, this question tests your ability to match migration strategies to strict constraints like compliance-driven code freezes and tight three-month timelines, where rehost’s speed and minimal disruption are critical. A common trap is confusing rehost with replatforming, which may involve minor optimizations that violate a no-code-change mandate. Remember the memory tip: “No code, no time, rehost is fine.”
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Rehost using AWS Application Migration Service (MGN) and Amazon EC2.
Rehosting (lift-and-shift) using AWS Application Migration Service (MGN) and EC2 meets the no-code-change requirement and can be completed within 3 months. Option A is wrong because retaining the application on-premises does not migrate it to AWS, failing the migration goal. Option C is wrong because replatforming to Amazon RDS would likely require code changes (e.g., database drivers, queries), violating the no-code-change constraint. Option D is wrong because refactoring into microservices requires significant code changes and is too time-consuming for the 3-month timeline.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Retain the application on-premises and use AWS Storage Gateway for backup.
Why it's wrong here
Retaining leaves the application on-premises, so the migration objective is unmet entirely. It is tempting because Retain with AWS Storage Gateway genuinely fits workloads that cannot move yet still need cloud-backed backup or hybrid storage.
- ✓
Rehost using AWS Application Migration Service (MGN) and Amazon EC2.
Why this is correct
Rehosting with AWS Application Migration Service lifts and shifts servers to Amazon EC2 without modifying code, satisfying the no-code-change compliance constraint. Block-level replication keeps the source running during cutover, enabling completion within the three-month window despite tight legacy coupling.
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Replatform to use Amazon RDS for MySQL.
Why it's wrong here
Replatforming introduces managed-service changes that violate the no-code-change compliance constraint, and RDS migration work cannot fit three months for a tightly coupled legacy stack. It is tempting because replatforming suits lift-tinker-and-shift moves where modest engine swaps are permitted.
- ✗
Refactor into microservices on Amazon ECS.
Why it's wrong here
Refactoring rewrites the application into microservices, directly breaching the prohibition on code changes and exceeding the three-month window. It is tempting because refactoring is the right strategy when long-term agility justifies a full redesign with no change restrictions.
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Same concept, more angles
1 more way this is tested on SAP-C02
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A company is migrating a critical application to AWS using the 7 Rs migration strategy. The application has a monolithic architecture and runs on a single large on-premises server. The business wants to reduce operational overhead but cannot afford any downtime. Which strategy should the solutions architect recommend?
hard- ✓ A.Rehost the application using AWS Application Migration Service
- B.Retire the application and replace it with a SaaS solution
- C.Replatform the application to use AWS managed services
- D.Refactor / Re-architect the application into microservices
Why A: Rehosting with AWS Application Migration Service (MGN) lifts and shifts the monolithic application to AWS with minimal changes and near-zero downtime through continuous block-level replication and a short cutover window. It reduces operational overhead by moving off physical hardware while preserving the application architecture, and it meets the no-downtime constraint because replication is ongoing until the final cutover. This is the recommended strategy when downtime is unacceptable and re-architecture is not feasible.
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This SAP-C02 practice question is part of Courseiva's free Amazon Web Services certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the SAP-C02 exam.