Prompt caching: what it does, when it helps and what it does not solve

Design for stable prefixes

Place reusable instructions, tools and documents in a stable order before highly variable content. Small changes near the start can prevent a match. Follow the provider’s current minimum size, retention and reporting requirements rather than assuming every repeated prompt is cached.

Measure cache performance

Track cache-write tokens, cache-read or cached tokens, hit rate and total cost. A high hit rate on a huge unnecessary prefix can still leave waste. A low hit rate may indicate unstable ordering or prompts that do not repeat enough.

Caching versus reduction

Varion keeps its proprietary engine implementation private. Commercial evaluation is based on measurable workload-specific outcomes, clear validation boundaries and customer-specific testing rather than disclosure of internal mechanisms. Use the dedicated Token Optimisation product area to evaluate whether the commercial result is suitable for your traffic; no universal performance percentage is promised.

Measurement checklist

1. Choose a representative completed task, not an artificial one-line prompt.
2. Record the selected model, provider input, cached input, output, retries and final result.
3. Change one optimization mechanism at a time so the cause remains visible.
4. Verify required identifiers, tool calls, code changes or business fields.
5. Keep passthrough available when the reduced request does not pass.

Varion commercial evaluation

Varion keeps proprietary product implementation details private. Evaluate Token Optimisation on representative traffic and judge it by the measured commercial result. New verified users receive 100,000 processed input tokens and 50 local test runs.