Key points
- Message Batches API: about 50 percent cost savings, up to a 24-hour processing window, no guaranteed latency.
- Appropriate for non-blocking, latency-tolerant workloads such as overnight reports, weekly audits and nightly test generation; inappropriate for blocking workflows such as pre-merge checks.
- A batch request cannot run multi-turn tool calling; tools cannot execute mid-request.
- custom_id correlates each request with its result and identifies which items failed.
- Submission cadence must be derived from the SLA: with 24-hour processing, submitting every 4 hours keeps a 30-hour commitment.
Skills the exam expects
- Match each workflow to the synchronous or batch API based on latency tolerance.
- Calculate batch submission frequency from SLA constraints.
- Resubmit only failed items, identified by custom_id, after fixing the cause (for example chunking oversized documents).
- Refine the prompt on a sample before batching large volumes to maximize first-pass success.
Common misconceptions
- "Batches usually finish quickly, so blocking checks are fine." There is no latency guarantee.
- "Results come back in order, so correlation is unnecessary." custom_id is how you match results to inputs.
- "Any agent workflow can be batched for half price." Tool loops within a request are not supported.
Watch for
- Moving a merge-blocking check to batch to save money.
- Resubmitting an entire batch because a few items failed.
- Submitting tens of thousands of items with an untested prompt.
Practice task 4.5
56 practice items cover this task in CCA Prep Studio: flashcards, matching, scenario questions and explain-it-back exercises, each tracked toward your mastery score.