The case for disaggregated LLM serving
The KV cache for a request is produced all at once during prefill, then consumed token by token during decode, so it's a natural place to cut the workload in two.. People usually think about it as a tool to tune time-per-output-token (TPOT) and time-to-first-token (TTFT) SLOs independently. I want to argue that, in practice, with sufficient load, and modulo many important implementation difficulties, you should always disaggregate.
- ▪The KV cache for a request is produced all at once during prefill, then consumed token by token during decode, so it's a natural place to cut the workload in two..
- ▪People usually think about it as a tool to tune time-per-output-token (TPOT) and time-to-first-token (TTFT) SLOs independently.
- ▪I want to argue that, in practice, with sufficient load, and modulo many important implementation difficulties, you should always disaggregate.
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| Original publisher | Doubleword |
| Canonical URL | https://blog.doubleword.ai/when-to-disaggregate |
| Publication time | Wed, 12 Aug 2026 08:46:51 +0000 |
| Retrieval time | 2026-08-12T08:51:30.355Z |
| Last seen | 2026-08-12T08:51:30.355Z |
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| Cluster | TyOVOcRFW35l · 1 stories |
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| Commercial reuse | May the content be reused commercially? | Not permitted |
Basis: Derived from the published RSS/Atom feed. Contact: [email protected]. Reviewed: 2026-07-24.
Opening excerpt (first ~120 words) tap to expand
←August 11, 2026Inference APIAPIThe case for disaggregated LLM servingFergus FinnFounder & Member of Technical Staff, DoublewordContentsWhat is disaggregated prefillHow to rate balanceThe conditions under which we can disaggregate properlyThe load vs. quantization effectsThe fabric sustains the KV cache production rateThe traffic balance can be trackedWhy it's strictly better, once the conditions are metConclusionAppendix: Space & UtilizationThe HBM tax that does existAttention-FFN disaggregationDisaggregated inference is an inference optimization technique in which we run prefill and decode on separate GPU pools, and ship the KV cache between them over the networkFirst laid out in DistServe and Splitwise.
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Excerpt limited to ~120 words for fair-use compliance. The full article is at Doubleword.
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