Project 1 — Basic LLM chatbot

• Build in this order.
• Each project extends a capability, not necessarily a separate repository.
• These are future learning projects; the notes remain in this one file.
• Move forward when you can explain the trade-offs and demonstrate the acceptance criteria, rather than after an arbitrary number of days.

Requirements

An authenticated user submits bounded text and receives an answer. Handle provider refusal, timeout, empty output, and missing configuration clearly.

Architecture

React → Node API → approved LLM → validated answer → React. React collects input, Node owns credentials and policy, and the model performs the language task.

Technologies

Existing MERN/Next.js stack, one provider SDK, Zod, normal backend logs. No agent framework is required.

Database design

• Conversation and message records with tenant/user ownership, roles, timestamps, prompt/model version, and completion status.
• Store only required content under a retention policy.

API design

POST /chat accepts a message and authorized conversation ID. Reject oversized input and return structured failure codes.

AI design

Clear system task and unknown behavior; bounded recent history; one model call. Begin with supplied-text explanation so no private facts need retrieval.

Security

Server-side credentials, session checks, scoped conversation reads, escaping in React, quotas, and redacted logs.

Evaluation

Test ordinary input, empty/large input, injected request, refusal, timeout, and invented account facts. Check usefulness and safe failure, not exact wording.

Observability

Request/model spans, latency, tokens, error category, task outcome, and safe run ID.

Deployment

Existing Node/container/serverless hosting with request limits verified and secrets configured. Separate development and production credentials.

Interview questions

• “Why no agent?” Answer: one language task needs one call.
• “How do you prevent client key leakage?” Answer: the browser calls authenticated backend routes and never receives the provider secret.

Acceptance: No key in the client bundle; unauthorized conversations fail; provider failure never produces a fabricated successful answer.