System Design: Securing Internal Microservices!
Keeping a microservice off the public internet is not enough. In Kubernetes, the network is flat by default, meaning every pod can talk to every other pod. If a hacker breaches your public marketing website, they are instantly inside your network and can call your internal payment service directly.
To fix this, you need three layers of defense. First, use Network Policies to block traffic between unrelated pods. Second, set up Mutual TLS (mTLS) using a service mesh like Istio so services check each other's certificates before sending data. Finally, add Authorization Policies so the Order Service can only call Payments and nothing else.
This zero-trust setup ensures that even if one pod gets hacked, your core internal services stay completely safe.
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