Build a mini RAG
Ship and explain the café FAQ retriever
Page 8 packages proved vs unproved evidence so another engineer can run, trust, or reject the five-document café FAQ retriever.
1Learn the idea
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Assemble the ship record
A shippable lab artifact includes: how to run it, the metric result (retrieval hit rate, citation correctness, supported-answer rate, abstention accuracy), the failure you can still reproduce (retrieval miss or ungrounded fluent answer), the security gate for prompt injection inside a stored FAQ note treated as instructions, and a rollback note. The user decision it supports remains: answer a café question only when a relevant local note is retrieved and cite its ID.
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Freeze the evidence
release={'docs_version':'faq-2026-07-18','gold_pass':3,'gold_total':3,'owner':'cafe-ops','rollback':'faq-2026-07-01'}
assert release['gold_pass']==release['gold_total'] and release['rollback']
print(release)
Expected evidence: stage evidence for mastery ship. Store this beside the fixture version so scores remain meaningful after content changes in build-mini-rag.
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Explain limits without apology
State operating limits for the café FAQ retriever in plain language: fixture size, offline vs live dependencies, and what would require a new eval set. Shipping build-mini-rag is honest scoping, not maximal confidence language.
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Lab notebook: proved vs unproved
Fill this table in your notes for the café FAQ retriever:
- Proved on
café notes: hours, wifi, pets, allergens, parking: … - Unproved beyond the fixture: …
- Metric that blocks release: retrieval hit rate, citation correctness, supported-answer rate, abstention accuracy
- Failure still reproducible: retrieval miss or ungrounded fluent answer
- Security gate: prompt injection inside a stored FAQ note treated as instructions
- Rollback: …
Ship the narrative only when the unproved list is honest. Reviewers trust narrow claims that support answer a café question only when a relevant local note is retrieved and cite its ID more than maximal language that collapses under the first production oddity.
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Worked judgment
Hand your ship note to a peer and ask them to recreate a proved/unproved ship note with rollback without watching you type. If they cannot, your evidence is still tribal knowledge. Tighten the run command and the metric line until a stranger can validate the café FAQ retriever against café notes: hours, wifi, pets, allergens, parking.
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Why this stage matters for the café FAQ retriever
At the mastery and shipping stage for build-mini-rag, the job is narrower than finishing a product demo. You are creating one progressive evidence piece about café notes: hours, wifi, pets, allergens, parking that later pages inherit without redefining success. Keep that fixture small enough to inspect by hand, keep outputs copy-pasteable as text, and refuse to narrate this baseline as if it were a production SLA: always-answer-from-largest-document heuristic.
For this page specifically, success looks like a proved/unproved ship note with rollback while still centering the user decision to answer a café question only when a relevant local note is retrieved and cite its ID. If you cannot point to a file, command, or assertion that proves that for the café FAQ retriever, stay on this page instead of advancing.
Go deeper
Before you start
Why this matters
List two things this chapter proved on the fixture and two things it did not prove about the café FAQ retriever. If you cannot name the gaps, you are not ready to ship the narrative—even if the code runs.
In the wild
See how this idea shows up as a product and a company — then come back to the lesson. Skills transfer across vendors.
Related lessons
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Page assessment
Answer from memory. Completion is saved from this evidence, not from opening the next page.
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