Prompt Caching and Cost Control in Java

Short summary

Prompt caching reduces LLM input costs by 90% for stable prefixes like system prompts and RAG context. Cache reads in Claude cost just 0.1× the base price while writes cost 1.25×, breaking even in two requests with 5-minute TTL. Anthropic's Java SDK includes cache_control configuration, usage metrics for verifying hits, and model routing strategies to escalate expensive queries only when needed.

• •Cache reads cost 0.1× base input price; writes cost 1.25× (5-min TTL) or 2× (1-hour TTL)
• •Minimum cacheable prefix is 4,096 tokens for Opus 4.8; implement via TextBlockParam.cacheControl()
• •Verify cache hits in usage metrics: cacheReadInputTokens > 0 means cache hit; 0 indicates cache miss or prefix mismatch

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