What is the difference between horizontal and vertical scaling in cloud security?

• A. Horizontal scales by increasing instance size; vertical scales by adding more instances.
• B. Horizontal scales by adding more instances; vertical scales by upgrading instance size.
• C. Horizontal and vertical scaling have identical security implications.
• D. Horizontal scales by increasing bandwidth; vertical scales by increasing storage.

Answer: (B)

Scaling in the cloud means handling more work either by adding more machines or by making a single machine more powerful. Horizontal scaling, or scale out, adds more instances to share the load. Vertical scaling, or scale up, increases the capacity of a single instance by upgrading its size (CPU, RAM, etc.).

In terms of security, this distinction matters. Adding more instances spreads the workload and can improve resilience, but it also expands the number of components you must secure, monitor, and patch consistently—so you need automated configuration, centralized logging, and strong identity controls across many nodes. Scaling up a single, larger instance reduces the number of moving parts, which can simplify management, but concentrates risk in one target and can hit resource and patching limits.

The statement aligns with the standard definitions: horizontal scaling adds more instances, while vertical scaling upgrades the instance size. The other choices misstate the direction of scaling, imply identical security implications, or reference unrelated metrics like bandwidth or storage.