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AI Systemscomplex complexity

AI Application Architecture

Architecture for production AI applications with model serving, RAG pipelines, evaluation, and cost controls that survive contact with real users.

7

Components

5

Considerations

3

Alternatives

complex

Complexity

Fit

When this blueprint fits

And when to walk away from it

When to use this

You are shipping LLM-powered features beyond a demo: a copilot, an assistant, a generation pipeline, or a workflow with model calls in the critical path. The right starting point when users will tolerate weirdness once but not twice.

When NOT to use this

If you only need a single feature with no streaming, no tools, and no evaluation needs, a direct provider SDK call is enough. Defer this architecture until you have at least three model call sites or one production-critical flow.

Architecture

System components

Key building blocks of this architecture, layered from infrastructure up.

01

LLM Gateway

A single internal interface for every model call with provider abstraction, fallbacks, caching, and cost tracking. Hardcoded OpenAI calls scattered through your codebase will hurt by month three when you want to A/B Claude against GPT. I keep this layer thin: a typed function per task, model selection per environment, and a shared retry policy. See OpenAI vs Anthropic.
Vercel AI SDKLiteLLMHeliconeCustom Gateway
02

RAG Pipeline

Retrieval-augmented generation with embedding pipeline, vector search, hybrid retrieval, and reranking. Most teams underinvest in retrieval quality and overinvest in prompt engineering. Get retrieval right (chunking strategy, hybrid search, reranking) and the prompts become much simpler. See the RAG playbook and the dedicated RAG blueprint.
PineconepgvectorOpenAI EmbeddingsCohere Rerank
03

Prompt Management

Version-controlled prompts with templating, A/B testing, and per-tenant overrides. Prompts are code: they need review, testing, and rollback. I store them in the repo as typed templates and let product change non-critical strings via a lightweight CMS layer.
Prompt TemplatesVersioningFeature FlagsPromptLayer
04

Evaluation System

Automated and human evaluation of model outputs with golden sets, regression suites, and LLM-as-judge metrics. The teams that ship reliable AI features have an eval suite that runs on every change. Without it you are guessing whether a prompt tweak made things better or worse.
RagasBraintrustLangfuseLLM-as-Judge
05

Cost Management

Per-tenant token tracking, budget alerts, semantic caching, and model selection by request class. AI cost can 10x overnight on a viral launch. Sample expensive features on free tiers, cache aggressive on read-heavy paths, and route cheap requests to small models. See the LLM cost insight.
Token MeteringSemantic CacheModel RoutingBudgets
06

Safety and Moderation

Input and output classification, jailbreak detection, and content filters tuned to the use case. The right level of moderation depends on the product. Customer support chat needs different filters than internal developer tools. Layered defence: input filter, system prompt, output filter, human review for high-risk responses.
OpenAI ModerationLlama GuardCustom Classifiers
07

Observability and Tracing

Full trace of every model call with inputs, outputs, latency, and cost. Debug a hallucination at 3am without traces and you will quit. Langfuse, Helicone, or Braintrust each handle this well, and the integration is one wrapper around your gateway.
LangfuseHeliconeBraintrustOpenTelemetry

Planning

Critical considerations

The things I have learned the hard way and would not skip on the next build.

Design for model provider changes. The leading model six months from now is not the leading model today. Keep your gateway provider-agnostic and your evals provider-agnostic so swaps are a config change.
Implement evaluation before production deployment. See the shipping AI features playbook. Build a golden set during prototyping and grow it from real user examples after launch.
Plan for cost at scale. Caching, model selection, and request batching matter more than prompt golf. A 30% cache hit rate on a popular feature pays for the engineer who built it.
Decide on streaming vs batched responses per feature. Streaming is a UX win for long generations and a cost hazard if you cannot tear down on disconnect. Wire your cancel paths.
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Options

Alternative approaches

Where I would consider a different shape entirely, with the trade-offs spelled out.

Alternative 01
LangChain or LlamaIndex for rapid prototyping when you want batteries-included primitives. Migrate off them once production demands more control.
Alternative 02
Vellum or Humanloop for managed prompt management with non-technical collaborator workflows.
Alternative 03
Modal or Replicate for managed inference when you need self-hosted models without the GPU operations.
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