Claude Message Batches API and Multi-Pass Review Design
Batch processing questions are pure judgement: when is cheaper-but-slower acceptable? The exam also asks how to design reviews that stay accurate at scale (Task Statements 4.5 and 4.6).
📦 Message Batches API facts
- 50% cost savings compared with synchronous calls.
- Processing can take up to 24 hours; no latency SLA.
- Results are correlated with
custom_id— they can arrive in any order. - No multi-turn tool calling inside a single request (tools can’t run mid-request).
- You poll for completion.
📦 Batch or synchronous?
| Use batches | Use synchronous calls |
|---|---|
| Overnight tech-debt reports, weekly audits, nightly test generation, historical backfills | Blocking pre-merge checks, live chat, anything a person is waiting on |
⏱️ SLA submission maths
If results are due within 30 hours and a batch can take 24 hours, a document arriving just after a submission waits until the next one. Submitting every 4 hours gives a worst case of 4 + 24 = 28 hours — inside the SLA. Every 8 hours (32 h) or 12 hours (36 h) can miss it.
🚨 Handling failures
Resubmit only the failed custom_ids, with a fix applied (for example, chunk documents that exceeded the context limit). Before a large run, refine the prompt on a representative sample to maximise first-pass success.
🔍 Multi-instance and multi-pass review
- Independent reviewer: a second Claude instance without the generator’s reasoning context catches more than self-review instructions or extended thinking in the same session.
- Multi-pass: per-file passes for local issues plus a cross-file integration pass.
- Confidence per finding: useful for routing reviewer attention once calibrated — not as ground truth.
🧪 Exam-Style Practice Questions
Try these before opening the answers. They use the same scenario style as the real exam.
Question 1. Which properties apply to the Message Batches API? *(Choose two)*
- A. Guaranteed 5-minute latency
- B. Multi-turn tool calling within a request
- C. 50% cost savings
- D. Results returned in submission order
- E. Up to 24-hour processing window
Show answer
Answer: C, E. A: there's no latency SLA. B: tools can't be executed mid-request. D: results can come back in any order, so correlate with `custom_id`.
Question 2. Results are due within 30 hours, and batches can take up to 24 hours to process. Which submission cadence safely meets the SLA?
- A. Every 8 hours
- B. Every 12 hours
- C. Every 4 hours
- D. Once a day
Show answer
Answer: C. The worst case is 4 h waiting plus 24 h processing = 28 h, which is under 30. B (36 h), A (32 h) and D (48 h) can miss the SLA.
Question 3. Why is an independent Claude instance better than self-review for generated code?
- A. It's cheaper
- B. Self-review is disallowed
- C. The generating session keeps its own reasoning context and is less likely to question its own decisions
- D. It uses a different tokenizer
Show answer
Answer: C. It removes anchoring on the original reasoning. A, B and D are false or irrelevant.
📝 Assignment
Do these tasks in order. Each one has a Done when check, so you know when it is complete. The stretch task is optional but close to what the exam expects from an architect. Keep your answers in one notes file or Git repository, and revisit them in your final week of revision together with the cheat sheet in the last lesson of this course.
- Task 1: Submit a batch of 20 requests with custom_id values and match the results by ID.
✅ Done when: All 20 results are matched to their requests by custom_id, even though they arrive in a different order. - Task 2: Calculate the submission cadence needed for a 30-hour SLA with 24-hour batch processing.
✅ Done when: Your answer is every 4 hours or more often, with the worst-case arithmetic written out. - Stretch: resubmit only failed requests after chunking the oversized inputs.
✅ Done when: Only the failed custom_ids are resubmitted, and the resubmitted requests succeed.
❓ Frequently Asked Questions
🤔 How much cheaper is the Message Batches API?
About 50% compared with standard synchronous calls.
🤔 How long can a batch take?
Up to 24 hours, with no latency guarantee.
🤔 Can I use batches for pre-merge checks?
No. Developers are waiting on those, so they need synchronous calls.
🤔 How do I match batch results to requests?
Use the custom_id you set on each request, because results can arrive in any order.
🏁 Summary
- Batches: 50% off, ≤ 24 h, no SLA, custom_id, no mid-request tools.
- Never put a blocking workflow on batches.
- Resubmit only failures; refine prompts on a sample first.
Next, continue with Claude Context Management: Case Facts, Lost-in-the-Middle and /compact.
Independent study material by SQA Tools. Not affiliated with, endorsed by or sponsored by Anthropic. Claude is a trademark of Anthropic. Mock questions are original practice items, not real exam content. Exam facts checked against Anthropic's official exam guides and certification FAQ on 11 November 2026.