Never trust a request by default, verify every time
Zero Trust is a security model that assumes no request internal or external should be trusted by default. Every service, user, and API call is authenticated and authorized on its own merits, rather than trusted because it originated inside a network perimeter.
Perimeter-based security fails the moment something gets inside the perimeter a compromised credential, a misconfigured internal service. Zero Trust limits the blast radius of exactly that scenario, because internal traffic is never implicitly trusted in the first place.
Least-privilege access control and service-to-service authentication are core to how we architect systems every service, API key, and role gets exactly the access it needs, reviewed as part of the build rather than bolted on afterward, as described in our security case study.