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Model Routing and Cascades

Model routing sends each request to the cheapest model that can handle it, escalating only when needed. Most production traffic is easy, so paying frontier prices for every request is usually the largest avoidable line in an AI bill. The engineering is in deciding cheaply and in knowing what to do when the router is wrong.

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RELATED CONCEPTS

AI Cost and Unit Economics Latency Optimization Inference-Time Compute Offline vs Online Evaluation Knowledge Distillation

LESSONS THAT TEACH THIS

The FDE EngagementCost per unit of their work is the number, and it decides the architecture25 min→Hard DeploymentsServe it from cache, send less, or send it somewhere cheaper30 min→

PRACTICE THIS IN REAL QUESTIONS

LLM & GenAI FundamentalsWhat is a token, and why should an FDE care about tokenization?→System Design & Production EngineeringWhat do p50, p95, and p99 latency actually mean, and why do production engineers obsess over the tail?→System Design & Production EngineeringEstimate the capacity and cost of an app with 50k DAU making 10 LLM calls each. What do you provision for?→System Design & Production EngineeringIt's 9am Monday and p99 latency is 10x normal. Walk me through your first 30 minutes.→Behavioral & Customer ScenariosEstimate: how many LLM tokens per day would a Fortune-500 customer-support org consume?→ML System Design (Product)Build a fraud-detection model for payments.→