Nosy Cache

What this cache coherence interview question tests

This is a medium-difficulty question on cache coherence protocols, a core topic in computer architecture that appears in systems and infrastructure interviews at firms building high-performance trading systems, databases, and low-latency infrastructure. It tests whether you understand how multiple processors maintain consistency when each has its own local cache.

A snoopy-cache protocol is one of the two main families of coherence mechanisms (the other being directory-based). To answer this question correctly, you need to recognize the defining characteristic: how caches observe and react to memory traffic on a shared bus. The question asks you to distinguish this approach from its alternatives and identify what makes it snoopy.

• Cache invalidation vs. update strategies
• Bus-based vs. directory-based coherence
• Write propagation and consistency models
• Scalability limitations of snooping approaches