- Updated: March 19, 2026
- 6 min read
Enforcing Per‑Tenant Billing with OPA and OpenClaw Rating API Edge – A Tactical Walkthrough
OpenClaw’s Rating API Edge can be combined with Open Policy Agent (OPA) to enforce per‑tenant rate limits and billing rules, while the built‑in multi‑tenant billing module handles usage aggregation and invoicing—all deployable on a UBOS‑managed Kubernetes cluster.
Introduction
OpenClaw is a powerful, open‑source rating engine that powers usage‑based monetization for SaaS platforms. The OpenClaw hosting solution on UBOS provides a production‑ready Kubernetes deployment, while the Rating API Edge adds a lightweight, high‑performance gateway for real‑time rating calls. When you need to serve multiple tenants from a single instance, multi‑tenant billing becomes essential, and OPA offers a declarative, policy‑as‑code framework to enforce tenant‑specific limits.
In this tactical walkthrough we will:
- Deploy the OpenClaw core services on UBOS.
- Install and configure the Rating API Edge.
- Enable the multi‑tenant billing module.
- Write OPA Rego policies for per‑tenant rate limiting and billing.
- Integrate OPA with the Rating API Edge via policy bundles and webhooks.
- Validate the end‑to‑end enforcement flow.
Prerequisites
Before you start, make sure you have the following tools and access rights:
- kubectl (v1.24+)
- Helm (v3.10+)
- OPA CLI (optional, for local testing)
- Admin access to a UBOS instance with a running Kubernetes cluster.
- Docker registry credentials for pushing custom images.
Architecture Overview
The diagram below illustrates the key components and data flow:
Requests from tenant applications hit the Rating API Edge, which forwards the call to OpenClaw’s rating engine. Before the rating is applied, the edge queries OPA for policy decisions (rate limits, discount eligibility, etc.). Billing events are captured by the multi‑tenant billing module and persisted for invoicing.
Step‑by‑Step Walkthrough
a. Deploy OpenClaw Core
Use the UBOS Helm chart to spin up OpenClaw services. The chart includes PostgreSQL, Redis, and the rating microservice.
helm repo add ubos https://charts.ubos.tech
helm repo update
helm install openclaw ubos/openclaw \
--namespace openclaw \
--create-namespace \
-f values-openclaw.yaml
Make sure values-openclaw.yaml contains your database credentials and any custom environment variables. For a quick start you can explore the UBOS templates for quick start.
b. Install Rating API Edge
The Rating API Edge runs as a sidecar proxy. Deploy it with the following Helm values:
helm install rating-edge ubos/rating-api-edge \
--namespace openclaw \
-f rating-edge-values.yaml
Key fields in rating-edge-values.yaml:
service.port: 8080 (exposed via Ingress)opa.enabled:true(activates OPA integration)billing.enabled:true(turns on multi‑tenant billing)
c. Configure Multi‑Tenant Billing Module
The billing module is a Helm sub‑chart that creates a billing-service and a billing-db. Add the following snippet to your rating-edge-values.yaml:
billing:
enabled: true
storageClass: standard
retentionDays: 90
tenantSelector:
label: tenant-id
UBOS’s Enterprise AI platform by UBOS provides built‑in observability for this module, so you can monitor usage per tenant from the dashboard.
d. Write OPA Policies for Tenant‑Specific Rules
Create a policies/ directory in your repo and add a Rego file named tenant_rules.rego:
# tenant_rules.rego
package openclaw.policy
default allow = false
# Extract tenant ID from request header
tenant_id = input.request.headers["x-tenant-id"]
# Rate limit per tenant (requests per minute)
rate_limit[tenant] = limit {
tenant = tenant_id
limit = data.rates[tenant]
}
allow {
# Check if the request is within the allowed rate
not over_limit
}
over_limit {
count := data.usage[tenant_id] # usage stored in Redis by the edge
count > rate_limit[tenant_id]
}
Store the policy bundle in a ConfigMap and mount it into the OPA sidecar:
apiVersion: v1
kind: ConfigMap
metadata:
name: opa-policy-bundle
data:
tenant_rules.rego: |
(contents of the file above)
---
apiVersion: apps/v1
kind: Deployment
metadata:
name: rating-edge
spec:
template:
spec:
containers:
- name: opa
image: openpolicyagent/opa:0.55
args:
- "run"
- "--server"
- "--bundle"
- "/policy"
volumeMounts:
- name: policy-bundle
mountPath: /policy
volumes:
- name: policy-bundle
configMap:
name: opa-policy-bundle
e. Integrate OPA with Rating API Edge
Configure the edge to call OPA’s REST endpoint before each rating request. Add the following to rating-edge-values.yaml:
opa:
url: http://localhost:8181/v1/data/openclaw/policy/allow
decision: allow
timeoutMs: 200
When OPA returns false, the edge responds with HTTP 429 (Too Many Requests) and logs the event for billing.
f. Test the Enforcement Flow
Use curl to simulate a tenant request:
curl -X POST https://rating.example.com/v1/rate \
-H "x-tenant-id: tenant-123" \
-H "Content-Type: application/json" \
-d '{"usage": 5}'
Expected outcomes:
- If the tenant is under the limit, you receive a
200 OKwith rating details. - If the limit is exceeded, the edge returns
429 Too Many Requestsand the billing module records the over‑usage event.
Code Snippets
OPA Rego Policy Example
# tenant_rules.rego (excerpt)
package openclaw.policy
default allow = false
tenant_id = input.request.headers["x-tenant-id"]
allow {
usage := data.usage[tenant_id]
limit := data.rates[tenant_id]
usage <= limit
}
Rating API Edge Configuration (YAML)
apiVersion: v1
kind: ConfigMap
metadata:
name: rating-edge-config
data:
config.yaml: |
server:
port: 8080
opa:
url: http://opa:8181/v1/data/openclaw/policy/allow
decision: allow
billing:
enabled: true
tenantLabel: tenant-id
Helm Values for Multi‑Tenant Billing
billing:
enabled: true
storageClass: fast-ssd
retentionDays: 180
tenantSelector:
label: tenant-id
invoice:
provider: stripe
currency: USD
Deployment Tips
- CI/CD Integration: Store your Helm charts in a GitOps repo and use Argo CD or Flux to automate rollouts. Include a
helm teststep that validates OPA policy compilation. - Monitoring & Logging: Leverage UBOS’s Workflow automation studio to pipe OPA decision logs into Loki and set up alerts in Grafana for rate‑limit breaches.
- Secret Management: Keep OPA bundle signatures in Vault and mount them via Kubernetes secrets to prevent tampering.
- Performance Tuning: Cache OPA decisions for 30 seconds using the edge’s built‑in cache to reduce latency.
- Common Pitfalls:
- Misaligned tenant IDs between the edge header and billing DB – enforce a naming convention.
- OPA policy syntax errors – run
opa checklocally before deployment. - Insufficient Redis memory – monitor
maxmemorysettings as usage grows.
Conclusion
By combining OpenClaw’s Rating API Edge with OPA and UBOS’s multi‑tenant billing module, you gain a fully declarative, scalable, and auditable monetization layer for any SaaS product. The approach delivers:
- Fine‑grained, per‑tenant rate limiting enforced at the edge.
- Automated usage aggregation and invoicing without custom code.
- Policy versioning and rollback via standard Git workflows.
- Observability through UBOS’s native monitoring stack.
Next steps include extending policies to cover discount rules, integrating with a payment gateway, and exploring AI marketing agents to personalize offers per tenant.
Further Resources
Explore additional UBOS capabilities that complement this setup:
- UBOS platform overview – deep dive into the underlying Kubernetes stack.
- UBOS pricing plans – choose the tier that matches your scale.
- UBOS partner program – get co‑selling and technical enablement.
- UBOS for startups – fast‑track your MVP.
- UBOS solutions for SMBs – tailored support for growing businesses.
- Web app editor on UBOS – prototype UI components for your billing portal.
- UBOS portfolio examples – see real‑world deployments.
- About UBOS – learn about the team behind the platform.
- Enterprise AI platform by UBOS – future‑proof your AI workloads.
For a complete, production‑ready OpenClaw deployment, refer to the official original integration guide.