Lesson 1 · 10 min
The LLM application stack
Every production LLM application is built from the same seven layers. Understanding the full stack — from user interface to model inference — lets you reason about where problems come from and where to invest.
The invisible architecture
Most engineers starting with LLMs think of the application as: prompt → model → response. That mental model produces prototypes. Production systems look nothing like it.
A customer support AI that handles 10,000 queries per day has a request router, multiple model tiers, a semantic cache, a retrieval layer, a guardrail layer, an orchestrator, a response formatter, a cost tracker, a trace store, and a fallback provider — all before the response reaches the user.
None of that complexity is accidental. Each layer exists to solve a real production problem. Understanding the standard stack means you can diagnose failures, make informed architectural decisions, and communicate clearly with the rest of the engineering team.