Building an Open Policy Agent Proof of Concept

The logs tell you why: Open Policy Agent evaluated the request against your rules and shut it down.

An Open Policy Agent (OPA) proof of concept shows, in the simplest possible way, how you can enforce policies across services without coupling security logic into application code. OPA is a lightweight, CNCF-graduated project that runs anywhere—sidecar, daemon, or embedded. It uses Rego, a declarative policy language, to describe what is allowed and what is not.

A focused proof of concept isolates one target system. It might be an HTTP API, a Kubernetes cluster, or Terraform plans. You wire OPA in as a decision engine. Your service sends structured input (JSON) to the OPA API endpoint. OPA matches the input against your Rego rules and returns a decision: allow or deny.

To build your OPA proof of concept:

1. Identify the service or workflow you need to control.
2. Define minimal policy that’s easy to understand—permissions, roles, resource constraints.
3. Install OPA in the desired mode. For Kubernetes, use the opa sidecar or gatekeeper. For APIs, run OPA as a local agent.
4. Create and load a Rego policy file.
5. Send test requests against the service. Validate whether OPA’s “allow” or “deny” matches your expectations.
6. Iterate quickly—adjust rules, reload policy—until your policy logic is stable.

For engineers who need compliance, access control, or safety checks before deploying code, an OPA proof of concept is the fastest way to see how policy-as-code works in real systems. You keep policies out of the application codebase, making them easier to audit and update. You gain consistent enforcement across multiple platforms, from cloud infrastructure to microservices.

Use logging and decision tracing during the proof of concept. OPA can produce detailed traces of how it evaluated every condition in a policy. These traces show why a request passed or failed—a crucial feature when debugging complex rules.

Once the OPA proof of concept is successful, the path to production is straightforward. Invite more systems to send OPA input for decision-making. Standardize policies across the organization. Keep policy repositories version-controlled, tested, and reviewed like application code.

You can see an Open Policy Agent proof of concept in action without wasting weeks on setup. Go to hoop.dev and deploy a live OPA environment in minutes. Test your rules. Watch them work.