Design Principles to Secure Application Development, Deployment and Maintenance

As part of our Best Practice series, we have pulled together a short set of design principles that are worth treating as non-negotiables in application development, deployment and ongoing maintenance. They work well as a project “definition of good”, and can be used in a few practical ways: as a design checklist, as part of design assurance reviews, or as prompts when shaping epics and acceptance criteria in an agile backlog.

The most effective way to apply these principles is to embed them into your software development lifecycle (SDLC), rather than bolting them on at the end. In practice that means: adopting secure coding standards, testing security continuously during development, and treating deployment and operations as part of the security boundary. Teams also need time and support to keep current—security patterns, threats and tooling change quickly—and applications should be reviewed regularly so that vulnerabilities are identified and addressed before they become incidents.

Below are the core principles we recommend as a baseline for securing application delivery. They are deliberately simple—because they need to be easy to remember, easy to test, and easy to apply under delivery pressure.

Key design principles for securing application development

1. Secure by Design
   Build security in from the start, not as a late-stage “hardening” activity. This includes authentication and authorisation, access control, secure defaults, and consistent input/output validation. Security decisions should be explicit in the design, reflected in the backlog, and verified during delivery.

2. Defence in Depth
   Assume a single control will fail and design multiple layers of protection. This might include encryption, network controls, service-to-service authentication, least-privilege access, runtime protections, and monitoring. The aim is to reduce the blast radius of an error, misconfiguration or compromise.

3. Least Privilege
   Grant only the minimum access needed for a user, service or component to do its job—and no more. This principle reduces the impact of credential compromise, limits lateral movement, and helps prevent accidental data exposure. It applies to human users, service accounts, workloads and third-party integrations.

4. Separation of Duties
   Avoid concentrating high-risk capabilities in a single role or component. Separate duties across people, teams and systems where it matters—especially for deployment approvals, production access, key management, and changes to security controls. This reduces both accidental and malicious misuse, and improves auditability.

5. Security Testing
   Treat security testing as a continuous activity, not a one-off gate. That includes code review, dependency and vulnerability scanning, configuration checks, and targeted penetration testing appropriate to the system and its risk profile. The goal is early detection and fast remediation, before release and before exposure.

These principles apply throughout the delivery lifecycle—design, build, test and deploy—and they map directly to practical controls you can adopt based on your context and risk appetite. The key is consistency: apply them repeatedly, make them visible, and build them into how teams deliver.

In our related technical guide, Security Checklist for NodeJS Development Design Assurance, we explore the controls that support these principles in more detail—looking at the practices and checks your full-stack/NodeJS delivery life-cycle should include as part of secure, repeatable delivery.

References

1. OWASP Secure Coding Practices – Quick Reference Guide