Every time an LLM application sends the same background context — system prompts, schema definitions, policy documents — without caching, it pays for that context all over again. At scale, across thousands of daily requests, that overhead compounds fast. This episode of Automatic unpacks the full guide to prompt caching for LLM applications, exploring how teams can dramatically reduce token spend and response latency while keeping output quality high — or even improving it. The episode covers the core mechanics of prompt caching and works through the practical architecture decisions, common failure modes, and design patterns that separate a well-built caching layer from one that quietly causes problems: What caching actually preserves — not full responses, but reusable intermediate artifacts like retrieval plans, chunk summaries, tool-call templates, and formatting scaffolds.Why quality can improve — caching deterministic steps removes variance from parts of a pipeline that should behave consistently, letting the model focus fresh generation where it actually matters.Where caching fits in real stacks — retrieval and grounding systems, tool-use orchestration, and structured generation each have distinct cacheable units and different risk profiles.Key design decisions — how to define the right cacheable unit, build cache keys that balance hit rate against staleness risk, and set expiration and invalidation policies that won't surprise the team during a model upgrade.Practical patterns that pay off quickly — intent normalization before routing, plan-then-execute splits that cache blueprints, and templated outputs with live-filled slots.The traps to avoid — over-caching personal or rapidly shifting context, hidden coupling between pipeline layers, and applying reuse in domains like legal or medical guidance where even structural similarity can mislead.The episode also addresses safety and trust: why cache hits should still pass through lightweight validators, how to log cache provenance for observability, and what privacy hygiene looks like when personal data and secrets are in play. The closing argument is that prompt caching, done with discipline, isn't an optimization hack — it's closer to craftsmanship, and the underlying pattern will remain valuable even as context windows and model capabilities continue to expand. For more on how AI is reshaping complex, document-heavy industries, listen to From Paper Stacks to Private LLMs: How Insurers Are Reinventing Claims. Automatic