credentials-operator VS bouncer

No more! The open-source intents-operator and credentials-operator enable you to achieve the same, except without all that work: do it all from Kubernetes, declaratively, and just-in-time, through the magic of IBAC (intent-based access control).

Otterize Credential Operator ( https://github.com/otterize/credentials-operator ) helps you automatically provision credentials as Kubernetes secrets (using a self-hosted SPIRE or a free SaaS solution). You can use pod annotations to determine the certificate's domain names (as well as many other properties). I think it is a straightforward approach to managing trust, especially for a relatively small cluster where you manage everything. (Full disclosure: I am one of the contributors to this project)

Have you taken a look at using SPIRE to create the TLS certificates and attesting about the workload identity? You could couple SPIRE server with the Otterize SPIRE integration operator to declaratively generate TLS certificates. This could be easier to deploy than a service mesh and sidecars, depending on your use case - what the clients are and what the servers are.

You could create JWT or mTLS-based identities, and then verify those in your middleware. If you are on Kubernetes, you might try using SPIRE together with the SPIRE integration operator to automatically issue identities as Kubernetes secrets, which you could then use to connect between services.

In practice, the technical part is implemented by the DevOps/platform team. The way in which you declare and get access to these secrets varies, but can be one of the cloud provider secret managers (e.g. AWS Secret Manager), Hashicorp Vault, or if you're on Kubernetes, could be something like cert-manager, Hashicorp Vault sidecars, or SPIRE coupled with the Otterize SPIRE integration.

If this seems a bit complicated, you could use SPIRE server to issue certificates and Otterize SPIRE integration operator to renew them in Kubernetes and update Secrets.

OPA is a full fledged solution as an external auth provider to reverse proxies like Nginx, Envoy or Traefik...etc. It can be a bit complex and overkill for smaller systems. I have a solution called bouncer as a much simpler and opinionated replacement to OPA. Have a look at it, at least it can give you ideas.