Guide · Cost Control
How to Limit AI API Usage Cost
AI API bills can explode overnight. Here's how to cap usage per user, set quotas, and monitor spend before it's too late.
Hard usage limits are how teams pass mandatory spend ceilings. Primary control: Cost Optimization
Tokens are a budget line, not a feature flag
Per-token pricing means one power user, one scraper, or one leaked key can empty the month. APRF Cost Optimization wants hard ceilings—per identity—plus alerts, not hope that the provider will warn you in time.
Teams have seen both: a user looping chat with no daily cap, and a client-side key scraped into five-figure weekend spend. Same fix family: proxy, wallet, alert.
Caps that actually bind
- Custody: model calls only from your backend
- Per-user / per-key quotas: tokens or requests per day in your DB
- Rate limits: short-window throttles so bursts die early
- Cache: identical prompts hit Redis before the model
- Alerts: provider spend at 50% / 80% / 100% of plan
Reject when the wallet is empty; don't silently keep calling.
Watch agent and context blowups
Unbounded tool loops and fat context packs burn the same meter as external abuse. Cap iterations and tokens per turn the same way you cap users—then review provider dashboards weekly even when alerts are quiet.
Next: Cost Optimization
Open the related pillar specification for mandatory checks, artifacts, and pass conditions. Self-attest is optional.
Related
Frequently asked questions
- How do I limit OpenAI API usage?
- Use a backend proxy to hold your API key. Implement per-user quotas (e.g., tokens per day), rate limiting, and caching. Set up billing alerts in the OpenAI dashboard.
- What causes high AI API bills?
- Leaked keys, no per-user limits, abuse, or high traffic without caching. A single user or bot can generate thousands in charges if unchecked.
- How do I set up AI API usage quotas?
- Track usage per user in your database. Before each request, check if the user has exceeded their daily quota. Reject or throttle requests above the limit.