Open source · MPL 2.0

Turn API limits into enforceable business policy.

Open-source edge engine for rate limits, quotas, and cost budgets — runs standalone or with a SaaS control plane for team governance.

Run the edge (OSS) See how it works

Sub-ms median · p99 < 1ms

No SDK changes needed

Kong · Envoy · Nginx · Traefik

Git-versioned policy

Core enforcement primitives for API governance.

Rate limits, budgets, and enforcement policies — as config, not code. Works for any API.

Unlike simple per-route rate limiting, Fairvisor enforces versioned, cost-aware, multi-tenant policies at the edge.

Rate Limits & Quotas

Per route, per key, per tenant — from JWT claims or headers.
One policy, enforced consistently at the edge.

Budgets

Cost-aware spend caps per key, team, or endpoint.
Throttle or cut off traffic when real usage crosses defined thresholds.

Noisy Neighbor Isolation

One tenant cannot degrade others.
Hard isolation via per-tenant limits and budgets.

Abuse Controls

Bot and crawler detection (ASN, fingerprinting signals).
Edge enforcement only — not a WAF, no payload inspection.

AI inference is just an expensive API. Token limits, cost budgets, and loop detection →

Policy as code. Not a backend hack.

Define policies in JSON, version in Git, validate in shadow mode, then promote with confidence.

Define

Versioned policies

Full version history and safe rollback. Policy changes are reviewed and deployed — not hidden in application code.

{
  "selector": { "path_prefix": "/v1/chat/" },
  "limit_keys": ["jwt:org_id"],
  "rules": [
    { "limit": "pro-tier" },
    { "budget": 500, "period": "1d",
      "unit": "USD" }
  ]
}

Test

Shadow mode

Limits are calculated but not enforced. See exactly which requests would be blocked before switching to hard enforcement.

fairvisor validate ./policies.json
fairvisor test --dry-run
# logs what would be enforced
# on your real traffic

Enforce

Edge enforcement

Sub-millisecond, in-process enforcement. If the control plane is unreachable, last-known policy remains active.

docker run -d fairvisor/edge \
  --config ./policies.json \
  --upstream http://your-api:8080

Policy-as-code via Git in v1 — SaaS adds review & approve UI and multi-environment deploy.

For teams running APIs in production

Open-source edge. Production-ready SaaS control plane.

The edge is free and runs standalone. The SaaS adds policy management, visibility, and team features.

Edge (open source, always free)

Reverse proxy or decision service mode
Sub-ms, in-memory enforcement
Fails open or closed — configurable
Prometheus metrics, Kubernetes-ready

SaaS control plane — why teams upgrade

Policy editor with validation
Fleet management
Analytics: top limited routes, tenants, abusive sources
Alerts (Datadog, Sentry, PagerDuty, Prometheus)
Audit exports for SOC 2 workflows
RBAC and SSO (Enterprise)

Fairvisor is not a WAF and not an API gateway replacement. It is a dedicated policy enforcement layer for API governance. Works with Kong / Envoy / Nginx / Traefik — see comparisons →

Adopted when API enforcement becomes a business problem.

Public APIs with paid tiers

You enforce Free / Pro / Enterprise tiers.
Hard limits at the edge — not best-effort checks in code.

Partner integrations

Each partner has its own contract.
Per-integration limits and kill switches enforced in real time.

Outgrown your API gateway's rate limiting

High-volume APIs where per-request gateway pricing no longer makes sense.
Keep your gateway. Add a dedicated enforcement layer.

Predictable failure

Deterministic enforcement: warn → throttle → reject.
No surprise overage at month end.

High-cost APIs (including AI)

When one request has real cost. Per-tenant budgets enforced before spend escalates. AI endpoints are just expensive APIs — enforce them with the same policy language. See AI enforcement →

Multi-tenant SaaS

One tenant's traffic spike shouldn't degrade service for others.
Hard per-tenant isolation enforced at the edge — not patched in application code.

What teams say

"Fairvisor lets us keep latency promises to users without burning unnecessary compute. Efficiency became a quality metric, not a compromise."

Max Usubyan CEO, thebutton.ai

"Growth is healthy only when it's predictable. Fairvisor made our API expansion controllable — in both performance and cost."

Sergey Shalaev CEO & Co-Founder, Solda.AI

5 minutes from zero to enforcement

Start in shadow mode, validate policy behavior, then switch to hard enforcement.

Read the quickstart guide

The edge engine is free and open source. See SaaS pricing →

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