Explain like I'm five · AI

What is Routing?

Model routing, told as a story about a guide parrot at the door that looks at each question and decides whether the small, medium or big parrot should answer.

hi!summarize thisreview this contractthe biggest parrotBILLhi → 100 beanssummary → 100review → 100beans explode!even a hello goes to the biggest parrot — the bill explodes

Every question goes to the biggest parrot — even a hello. The bill explodes.The big parrot spends many beans per answer. If a hello, a summary and a contract review all cost the same, the bean bill piles up fast.

only the big parrothi!100 beans100 beans for a hello — wasteonly the small parrotreview this contractum… looks fine?too small for hard work — shorteach question needs a different size — one bird means waste or shortfall

Each question needs a different size of parrot. One bird for everything means waste or shortfall.The big parrot knows more, is slower and pricier; the small one is fast and cheap but short on hard work. Give a hard one to the small bird and a plausible wrong answer goes out.

GUIDE BOARDeasy → small parrotmedium → medium parrothard → big parrotit looks first, at the doorthe guide parrotsmall · 1 beanmedium · 10 beansbig · 100 beansrouting: a guide parrot at the door looks at each question and picks small, medium or big

Routing is a guide parrot at the door looking at each question and picking the small, medium or big parrot.The guide parrot reads the question and tags it easy, medium or hard. Sent by tag, easy ones get answered cheaply and hard ones properly. The guide itself is a tiny bird, or just a few lines of note.

Easy → small parrothellos, short answers, sorting
Hard → big parrotlong reasoning, law, code
Not sure? Pass it upsmall → big (fallback)
Draw the line with testshow far the small bird goes
hi!1 beansummarize this10 beansreview this contract100 beansALL TO THE BIG100 + 100 + 100= 300 beansROUTED1 + 10 + 100= 111 beanssame answers, a third of the beansthe small parrot does easy ones just as wellthe right size per question — same answers, far fewer beans

Send each question to the right size and the answers stay the same while the beans drop a lot.The small parrot is also quicker — a shorter answer time. In a multi-step errand list, each step can pick a different parrot.

when the guide is wrongreview this contractguidethinks it is easyum… looks fine?quality leaks — a wrong answer goes outso: fallback and testsnot sure!pass upTESTsmall ✓ 80%tests measure how far the small parrot can gonot sure → pass it to the big onethe guide gets it wrong too — so fallback and tests go with it

The guide gets it wrong too. Mistake hard for easy and quality leaks. So fallback and tests go with it.When the small bird says not sure, pass it to the big one (fallback). And the examiner measures how far the small bird can go. If leaked quality outweighs the saved beans, you lose.

In one breath

Routing = a guide parrot at the door decides whether the small, medium or big parrot answers each question. Easy ones cheaply, hard ones properly. The guide errs too, so fallback (not sure → big bird) and tests go with it.

Classifying each request by difficulty or type and sending it to the right model (small, medium, large) to cut cost and latency. The classifier is a small model, rules, or a prompt; when the small model is unsure it escalates to a larger one (fallback, cascade). An evaluation set decides how far the small model can go, and you keep checking that quality lost on misrouted requests doesn't outweigh the savings.

When grown-ups say it

Model routing
The guide parrot. Looks at the question and picks the small, medium or big parrot.
Classifier
Tagging questions easy or hard. A tiny parrot or a few rules. It has to be fast and cheap.
Fallback
Passing it up when unsure. When the small bird says it doesn't know, the big bird answers again. It catches the guide's mistakes.
Cascade
Small bird first, then the next. Escalate small → medium → big. Most questions end at the small bird.
Cost optimization
Saving beans. Not using the big bird for easy questions is the biggest saving. → the bean bill
Latency
Time until the answer arrives. The small parrot is much faster. → what answering costs and takes
Evaluation
Measuring how far the small bird goes. Route without tests and you won't see quality leaking. → the examiner's scorecard
Workflow
A different parrot per step. Each step of the errand list picks its own bird. → the errand list
Next story
Caring for the Parrot →
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