TTFT vs generation time: caching, smaller models, parallelism, and speculative tricks.
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What techniques reduce LLM latency at each stage of a request?
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01
Understand the problem
latencyttftperformanceoptimization
02
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Split latency into time-to-first-token (prompt processing + queueing) and generation time (output tokens x per-token time). Reduce TTFT with prompt caching, shorter prompts and warm capacity; reduce generation time with smaller/faster models, capped or more concise outputs, and predicted-output/speculative techniques w
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04
Read the code
Parallelize independent LLM work
// sequential: ~3× the latency of the slowest call
// parallel: bounded by the slowest call only
const [summary, sentiment, entities] = await Promise.all([
small.complete({ prompt: summarize(doc), maxTokens: 200 }),
small.complete({ prompt: classifySentiment(doc), maxTokens: 5 }),
small.complete({ prompt: extractEntities(doc), maxTokens: 300 }),
]);
// and route: only escalate the hard path to the frontier model
const answer = needsDeepReasoning(query)
? await frontier.complete({ prompt })
: await small.complete({ prompt });05
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