We are moving our Dev, Staging, and Production environments into a single large Kubernetes Cluster to save on costs. How do we ensure that a bug in a Dev container doesn't allow it to "reach out" and connect to the Production database? Does a Namespace provide a hard security boundary, or do we need additional layers like RBAC and firewall-like rules?
3 answers
Namespaces are only a logical "folder" for organization; they are not a security boundary by default. To secure them, you first need RBAC (Role-Based Access Control) to limit who can see which namespace. Then, you must implement Network Policies. These act as a built-in firewall, allowing you to say "Only Pods in the prod-frontend namespace can talk to the prod-db namespace."
By default, Kubernetes has an "Allow All" network policy—meaning any Pod can talk to any other Pod in the cluster, regardless of the namespace. The best practice is to start with a Deny-All policy for all ingress/egress and then explicitly "whitelist" only the connections your application actually needs to function.
You should also look into Resource Quotas per namespace. This ensures the Dev team doesn't accidentally spin up massive instances that consume all the CPU/RAM, effectively causing a "Denial of Service" for the Production environment running on the same hardware.
We use Quotas religiously. It’s the only way to keep our cloud bill predictable when you have 20 different teams deploying to the same cluster. It forces everyone to optimize their Resource Limits.
This is the "Zero Trust" approach. It's more work upfront, but it prevents a compromised web server from becoming a gateway for an attacker to scan your entire internal cluster network.