🐳 Containerizing a Python FastAPI Application with Docker (and Solving ARM vs x86 Architecture Issues)

When working with containerized applications, Docker usually makes deployments predictable and consistent. Once everything is packaged inside a container, the expectation is simple: “If it works on my machine, it should work everywhere.” However, real-world environments sometimes introduce subtle issues — especially when applications are built on machines with different CPU architectures, such as x86 (AMD64) and ARM64. Recently, I was containerizing a small Python FastAPI application, and I noticed something interesting. The Docker image worked perfectly on my Ubuntu server but behaved differently on another machine. After some investigation, the root cause turned out to be architecture differences between systems. In this article, I'll walk through the entire process: Containerizing a FastAPI application with Docker Running the application using Docker Compose Understanding ARM vs x86 architecture differences Troubleshooting Docker daemon issues Building multi-architecture images If y