Do I need policy enforcement for all public APIs?

Usually yes—you want some form of policy enforcement on every public API, because public endpoints are the main place where authentication, authorization, rate limits, input validation, and abuse protection matter.

That said, it doesn’t always mean a heavy policy engine at every layer. A practical approach is:

• At the edge / gateway: enforce broad policies like auth, rate limiting, request size limits, IP reputation, and schema validation.
• At the service/API level: enforce authorization, tenant isolation, resource-level permissions, and business rules.
• For internal-only or low-risk endpoints: you may use lighter checks, but they should still be covered by baseline controls.

Why it matters

Public APIs are exposed to:

• unauthorized access
• data exfiltration
• abuse and scraping
• brute-force and credential stuffing
• broken object-level authorization (BOLA/IDOR)
• injection and malformed payloads

Minimum baseline for public APIs

I’d strongly recommend:

• authentication
• authorization
• input validation
• rate limiting / throttling
• logging and auditing
• TLS everywhere
• clear error handling
• quotas for expensive operations

When you might not need “full” policy enforcement everywhere

If by “policy enforcement” you mean a centralized policy engine like OPA or a gateway-based policy layer, then:

• Not necessarily on every endpoint
• But every endpoint must still be governed by policy, even if implemented in code or middleware

Simple rule

If an API is publicly reachable, assume it needs policy enforcement unless it is:

• strictly anonymous by design
• read-only and non-sensitive
• heavily rate-limited
• low risk and well sandboxed

If you want, I can also give you a recommended policy model by API type (public, partner, internal, admin).