Veo 3 launched at Google I/O just a few weeks ago, and since then we’ve seen countless videos go viral, delighting millions of people and demonstratin...
Two reasoning tiers, one routing decision
OpenAI's o3 and o4-mini are both reasoning models, meaning they spend extra computation working through a problem before they answer rather than replying in a single pass. The practical difference between them is not what they can attempt but how much effort and latency each one costs per request. o3 is the heavier tier aimed at harder problems, while o4-mini is the lighter, faster tier meant to handle the bulk of everyday reasoning work. For a production system, the real question is not "which model is better" but "which requests deserve which tier."
Treat the two as a routing problem. Most traffic in a typical application is repetitive and well-bounded, and a smaller reasoning model resolves it quickly. A minority of requests are genuinely hard, ambiguous, or high-stakes, and those are worth the extra cost and wait of the larger tier.
When o4-mini is the right default
Start with o4-mini as your default and only escalate when you have a reason to. Because it reasons faster and costs less per call, it keeps latency low enough for interactive features and keeps the bill manageable when volume is high. It handles structured tasks, moderate multi-step logic, and requests where the answer can be checked cheaply after the fact.
Good candidates for the smaller tier share a few traits:
- The input is well-formed and the task is clearly specified.
- A wrong answer is recoverable — it can be retried, validated, or corrected downstream.
- Latency matters because a human is waiting on the response.
- The request is one of many near-identical ones, so per-call cost compounds.
Reserving o3 for the hard cases
Escalate to o3 when the cost of a wrong answer outweighs the cost of extra reasoning time. That includes long chains of dependent steps, problems where subtle mistakes cascade, and tasks where you cannot easily verify the output yourself. Because o3 spends more effort per request, use it deliberately rather than as a blanket default — routing everything to the heavier tier erases the efficiency the smaller one gives you.
A workable pattern is to let o4-mini attempt first, then fall back to o3 only when a confidence check, a validation step, or a failed self-consistency test flags the answer as unreliable. This keeps most traffic cheap while still catching the cases that need more thought.
Putting reasoning tiers into production
Before switching a live feature to either model, build the measurement around it. Log which tier handled each request, how long it took, and whether the output passed your validation, so you can see where escalation actually helps versus where it just adds latency and cost. Reasoning models can also spend a variable amount of effort per request, so set expectations for timeouts and budget accordingly rather than assuming a fixed response time.
Keep the routing logic explicit and adjustable. As you gather data on which request types benefit from o3, you can tighten the rules that decide when to escalate, and you can shift more traffic back to o4-mini as you gain confidence that it handles a given case well. The goal is a system where the expensive tier earns its keep on the requests that need it and nowhere else.