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prompt-cache-optimizer

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Optimize token usage through prompt caching and compression

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How to use this skill

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Source SKILL.md: https://github.com/Miosa-osa/canopy/blob/HEAD/library/skills/ai-patterns/prompt-cache-optimizer/SKILL.md

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Prompt Cache Optimizer Skill

Reduces token costs by 50-90% through intelligent caching and compression.

When to Activate

  • Large context windows (>50K tokens)
  • Repeated similar queries
  • Long-running sessions
  • Cost-conscious operations

Optimization Layers

Layer 1: Semantic Caching

Query → Embedding → Similarity Search → Cache Hit/Miss
         ↓              ↓
    Vector Store    Return cached or call LLM

Cache hits provide 100% token savings with near-instant response.

Layer 2: Prompt Compression (LLMLingua-2)

  • Light: 2-3x reduction, <5% accuracy impact
  • Moderate: 5-7x reduction, 5-15% accuracy impact
  • Aggressive: 10-20x reduction, requires validation

Layer 3: Strategic Context Placement

Mitigate "lost in the middle" problem:

  • Place most important information at START and END
  • Middle content has 30-50% lower retention

Layer 4: Hierarchical Memory Tiering

Working Memory (registers)  → Always in context
FIFO Queue (L1/L2 cache)    → Recent exchanges
Archival Memory (disk)      → Semantic search only

Implementation Workflow

  1. Check semantic cache before any LLM call
  2. Compress context using appropriate level
  3. Structure placement - critical info at boundaries
  4. Tier management - evict low-importance content
  5. Cache response for future queries

Compression Decision Matrix

Context SizeLatency NeedAccuracy NeedStrategy
<10K tokensAnyAnyNo compression
10K-50KLowHighLight (2-3x)
10K-50KHighMediumModerate (5-7x)
50K-100KAnyMediumAggressive (10-20x)
>100KAnyAnyHierarchical + Aggressive

Key Patterns

Attention Sink Preservation

For streaming/long sessions, preserve first 4 tokens as attention sinks:

[attention_sinks (4 tokens)] + [rolling_window (window - 4)]

This maintains model coherence over infinite context.

Hybrid Search for RAG

Hybrid = Dense (semantic) + Sparse (BM25)
Fusion = Reciprocal Rank Fusion (RRF)

Achieves 50-100x document reduction with maintained relevance.

Metrics to Track

  • Cache hit rate (target: >60%)
  • Compression ratio achieved
  • Accuracy impact (sample validation)
  • Token savings per session
  • Latency impact

Integration Points

  • Pre-prompt: Apply compression
  • Post-response: Cache result
  • Session start: Load cached context
  • Memory pressure: Tier eviction

Based on LLMLingua, GPTCache, MemGPT, and StreamingLLM research