Act as a senior DevOps engineer with 5+ years of experience in containerization and cloud deployments. Provide a step-by-step guide on how to use Docker for containerizing a [WEB APPLICATION/MICROSERVICE/DATABASE], including best practices for optimizing [PERFORMANCE/SECURITY/SCALABILITY]. Cover essential commands, Dockerfile configurations, and troubleshooting common issues like [NETWORK ERRORS/IMAGE BLOAT/PORT CONFLICTS]. Ensure the guide is beginner-friendly but includes advanced tips for experienced users. Use real-world examples where possible.