4Application Deployment and Security

• 4.1Deployment models and types

  Frames "where to run an app" as choosing among the private / public / hybrid / edge cloud models, edge computing (processing near the data source), and the runtime substrate—virtual machine (VM), bare metal, and container—as the judgment of "which fits this requirement (latency, isolation, performance, portability)."

• 4.2CI/CD and containers

  Covers the CI/CD pipeline that delivers code safely (automating build -> test -> deploy), the unit tests that guard changes (Python unittest/pytest), and the Dockerfile (FROM/RUN/COPY/CMD/EXPOSE) plus the image-and-container relationship that makes an app portable—framed as reading/diagnosing "what this pipeline/Dockerfile guarantees, and where it is wrong."

• 4.3Application security

  Covers secret management for handling credentials safely (environment variables/secret stores, never committing plaintext) and encryption (at rest and in transit), the roles of the firewall, DNS, load balancer, and reverse proxy, and the representative OWASP threats (XSS, SQLi, CSRF)—framed as diagnosing "what this handling protects and where the hole is."

• 4.4Operations and practice

  Covers the basic bash commands used in deployment/operations (file/directory ops—ls/cd/pwd/mkdir/cp/mv/rm/cat, and environment variables export/env) as reading "what this command sequence does," and the DevOps principles (culture, automation, measurement, sharing) as the judgment of "why this practice creates value."