MERN and AI

Beginner — Where does the LLM call belong?

• In a server-side AI service behind authenticated Node/Next.js routes.
• React sends bounded input and receives safe text/events; provider secrets and trusted instructions stay on the backend.

Intermediate — How do MongoDB, Redis, and a vector index differ?

• MongoDB stores application documents and canonical records where appropriate.
• Redis provides scoped caching/counters/queue backing.
• A vector index serves derived retrieval representations; none should silently replace authoritative claim-service truth.

Senior — How do you structure the backend?

• Separate identity/validation, AI context and provider adapters, retrieval, safe tools, and domain services.
• Add queues or a graph only when state/recovery demands them.
• Keep business contracts independent of whichever framework coordinates the conversation.

Scenario — A React chat UI renders malicious generated HTML. What changes?

• Render model content as escaped text or a sanitized restricted Markdown subset.
• Do not trust generated HTML or links automatically.
• Review XSS, source URLs, attachment access, and leaked internal events alongside the backend controls.