Batch API vs prompt caching: which saves more?
These two levers are often confused. They target different waste and, crucially, they combine: a batched request with a cached prefix gets both discounts.
Caching targets repetition
Caching saves on repeated input — the same prefix sent many times. If your prompts are large and stable, caching is your biggest lever.
Batch targets latency tolerance
Batch saves 50% on anything that doesn't need an immediate answer, on both input and output. If a lot of your spend is background jobs, batch is your biggest lever.
They stack
You don't have to choose. A non-urgent, repetitive workload should use both — the batch discount applies on top of the cache discount.
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