Cost and Reliability
Manage AI cost, latency, error budgets, rate limits, fallback, and workload classes.
Written and reviewed by Eric Han · Co-founder & CTO, reopt
Key takeaways
- AI cost and reliability are coupled: a cheaper route may miss quality targets while a stronger route breaks latency or budget targets.
- Classify work into workload classes such as customer synchronous, customer async, internal productivity, batch enrichment, and critical automation, each with its own reliability posture.
- Track cost per successful task, latency by model and route, error and fallback rate, queue depth, quality by workload, and budget burn.
- Set budget alerts, route-level caps, model fallback rules, and kill switches before usage scales.
Separate compute billing, limits, and request budgets
Fluid Compute is billed on Active CPU, Provisioned Memory, and Invocations. Waiting for a model is not the same as burning CPU, while memory, invocations, model tokens, Sandbox, and Workflow still contribute to cost.
The 300-second function default and plan maxima are platform limits. Set a separate customer-facing latency SLO and bounded fallback deadline. Verify Beta requirements before relying on 30-minute execution or 5 GB bundles. Threshold examples below are team policy, not a Vercel SLA.
Fluid Compute pricing · Functions limits.
AI cost and reliability are linked. A cheaper route may fail quality targets; a stronger route may break latency or budget targets. Platform teams need workload classes.
Workload Classes
| Class | Reliability posture |
|---|---|
| Customer synchronous | Low latency, fallback, strict monitoring |
| Customer async | Durable workflow, progress, retry |
| Internal productivity | Cost-aware route and graceful failure |
| Batch enrichment | Queue, throttle, low-cost model |
| Critical automation | Approval, audit, rollback, strong model |
Operating Metrics
- Cost per successful task.
- Latency by model and route.
- Error and fallback rate.
- Queue depth and job age.
- Quality score by workload.
- Budget burn by project or team.
Guardrails
Set budget alerts, route-level caps, model fallback rules, and kill switches before usage scales.