CV0-004 Cloud Architecture and Design Practice Question
A company is migrating a legacy stateful application to the cloud. The application currently runs on a single server and stores session data locally. To enable horizontal scaling, which two design changes should the architect recommend? (Select TWO.)
⚠ Common exam trap
The trap is treating sticky sessions as a scaling solution — they preserve session continuity but actually inhibit horizontal scaling and are the opposite of the stateless design the question is asking for.
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
✓
Move session state to a shared database or cache
Option C is correct because moving session state to a shared database or cache (e.g., Redis, Memcached, or DynamoDB) externalizes the state so any instance behind the load balancer can serve any request, which is essential for horizontal scaling. Option E is correct because refactoring the application to be stateless removes local session dependencies entirely, allowing instances to be added or removed freely and making the tier truly horizontally scalable. Options A and D are incorrect because adding storage or using a larger instance are vertical scaling approaches that do not enable horizontal scaling and leave the stateful single-server bottleneck in place. Option B is incorrect because sticky sessions only pin a client to one instance, which preserves the stateful coupling, can cause uneven load, and does not solve the underlying need to share or eliminate session state.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Add more storage to the existing instance
Why it's wrong here
Adding storage to the existing instance addresses disk capacity, not session locality, so the application still runs on one server and cannot scale out. It tempts because storage exhaustion often accompanies stateful growth, and it is correct when the bottleneck is genuinely disk space on a single node.
- ✗
Implement sticky sessions on the load balancer
Why it's wrong here
Sticky sessions pin each user to one backend, so session data stays local and instances cannot be added or replaced freely, defeating horizontal scaling. It tempts because it is the standard quick fix for stateful web tiers, and it is correct when sessions must remain in-process and shared storage is unavailable.
- ✓
Move session state to a shared database or cache
Why this is correct
Moving session state to a shared database or cache externalises it from individual instances, so any server behind the load balancer can serve any request. This directly satisfies the horizontal scaling requirement, since locally stored sessions would otherwise pin users to one server and break scaling.
- ✗
Use a larger instance type for the application server
Why it's wrong here
Vertical scaling enlarges one server's capacity, leaving session state bound to that single node, so horizontal scaling and distribution across instances remain impossible. It tempts because resizing is the quickest fix for a saturated single server, and it is correct when the workload genuinely cannot be partitioned and must stay on one machine.
- ✓
Refactor the application to be stateless
Why this is correct
Refactoring to stateless removes locally held session data, which is the specific blocker to horizontal scaling in the stem. Once no instance owns session state, any replica can serve any request, so the load balancer can distribute traffic freely. Externalise sessions to a shared store such as a database or cache.
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Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official CompTIA exam blueprint
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