What are Multi-Query (MQA) and Grouped-Query Attention (GQA), and why do they exist?
MQA and GQA shrink the KV cache, the thing that bottlenecks LLM serving. The signal is understanding they share key/value heads across query heads to trim memory and bandwidth, with GQA as the quality-preserving middle ground. Here is the answer.
Updated Sep 2026 · Grounded in real GenAI, LLM, and AI/ML engineering interview loops and written to a senior-engineer editorial bar.
MQA and GQA shrink the KV cache, the thing that bottlenecks LLM serving. The signal is understanding they share key/value heads across query heads to trim memory and bandwidth, with GQA as the quality-preserving middle ground. Here is the answer.
Lead with where the obvious approach breaks, because that is the judgment they are screening for — most candidates jump straight to the happy path and lose the room.
Then walk the failure back through the pipeline in order, naming the one metric the customer's exec sponsor actually cares about before you propose the fix.
