Prompt Prefix Reuse Cuts SLM Processing Time 57% With 145-Token Cache
Updated
Updated · KDnuggets · Sep 18
Prompt Prefix Reuse Cuts SLM Processing Time 57% With 145-Token Cache
1 articles · Updated · KDnuggets · Sep 18
Summary
A key-value cache for a static 145-token prompt prefix cut runtime to 80.07 seconds from 184.85 seconds across 600 support-ticket classifications, lowering average latency to 133.5 ms from 308.1 ms.
The gain came from computing the fixed instruction block once and feeding the model only each ticket’s changing suffix, instead of re-encoding the full 167-token prompt on every call.
In the test setup, 87% of each prompt was unchanged, and the cached path matched the full re-encoding path on all distinct tickets, making the speedup a pure compute optimization rather than a behavior change.
The article says the benefit should grow as prompts become more static and instruction-heavy, improving the practicality of 0.5B-class small language models for narrow automation tasks.