Securing microservices at scale involves implementing five key strategies: building complete architecture visibility, applying zero trust authentication, creating defense in depth, automating security throughout the CI/CD pipeline, and enabling real-time monitoring and incident response. Visibility is crucial as it identifies unmonitored attack vectors and undocumented dependencies, while zero trust authentication eliminates implicit trust by verifying every request between services. Defense in depth employs multiple layers such as API gateways, web application firewalls (WAFs), and network segmentation to thwart potential breaches. Automation in the CI/CD pipeline ensures rapid detection and remediation of vulnerabilities, and real-time monitoring allows for prompt threat detection and response, significantly reducing the average detection time from days to minutes. These practices, when implemented incrementally, can lead to measurable security improvements within a short period, supporting organizations in building resilient microservice architectures.