How can a large organization achieve 100% uptime and zero security breaches at a massive scale? It requires moving past standard management techniques and focusing on a critical metric: maintainability. At the recent Red Hat OpenShift Commons Gathering in Amsterdam, ING senior engineers Robbin Siepman and Rob de Boer revealed the maintainable architectural blueprint behind one of the financial sector's most resilient cloud-native estates.ING is a global financial institution that serves nearly 40 million customers across 100 countries. One of the bank’s main missions is to maintain the ING Hosted Container Platform (ICHP), a massive estate of 400 servers and 23,000 physical cores, with a lean team of fewer than 30 people. Here are the four pillars of maintainability that drive the company’s strategy.Pillar 1: Zero privilege and automated complianceThe first rule of ICHP is simple: no humans allowed.ING has eliminated human interaction with its clusters to ensure stability. Even administrators lack permanent access; SSH is disabled across the entire estate. Instead, every change is funneled through CI/CD pipelines.Automated testing: Pipelines handle compliance checks and vulnerability scanning before code ever touches a namespace.Traceability: Every production change requires an approved change in the configuration management database (CMDB), which requires a test plan and fallback mechanisms. Resources are automatically registered in the CMDB.Statelessness: By keeping the clusters stateless and access-free, the team minimizes the configuration drift that often leads to outages.Pillar 2: Namespace-as-a-Service ING’s sweet spot for balancing developer freedom with bank-grade security is its Namespace-as-a-Service (NaaS) model.Developers are free to deploy what they need, within the framework of internal guardrails and 12 Factor Application principles. In particular, applications must be declarative, automated, and strictly stateless. If an application needs to persist data, it must use external services like Cassandra or object storage rather than the platform itself.