Bedrock prompt caching: writes cost 25% more, reads 90% less, 1-hour TTL doubles the write premium.

AWS published the arithmetic builders need to decide whether caching pays. A 10,000-token document reused across 10 questions nets roughly 75% off total input cost. Minimum checkpoint size is 1,024 tokens for Claude Sonnet 4.5 and 4.6, 4,096 for Opus. Default TTL is 5 minutes, simplified cache management covers about 20 preceding content blocks per checkpoint, and multiple checkpoints must be ordered longest TTL to shortest. Time-to-first-token gains become pronounced past 10,000 tokens.