Top 3 Scalability Interview Questions
Browse 3 real-world technical and behavioral interview questions about Scalability. Review scenarios, edge cases, and architectural best practices.
How do you handle cache invalidation, and what goes wrong at scale?
Pick a write policy that matches your consistency requirement rather than treating invalidation as an afterthought, then defend against the three failure modes that only appear under load: stampede on expiry, staleness from lost invalidation messages, and unbounded growth from missing eviction.
A stakeholder tells you the system must be scalable. How do you turn that into a requirement you can design and test against?
Rewrite it as a quality-attribute scenario: a named stimulus arriving at a stated rate, hitting a stated system state, with a response measured at a percentile over a defined window. A number with a load figure, a duration and a named sacrifice is designable and testable; a list of maxima is not.
What problem do virtual threads actually solve, and when do they not help?
Virtual threads make blocking cheap by unmounting from their carrier OS thread whenever they block, so thread-per-request scales to hundreds of thousands of concurrent tasks. Finalised in JDK 21, they do nothing for CPU-bound work, and pooling them defeats their purpose.