Docker multi-stage builds cut image size from 823MB to 11MB

Docker images built with a single-stage Dockerfile often ship unnecessary build tools — such as compilers and dev dependencies — that are not required at runtime, bloating production images significantly. Multi-stage builds solve this by allowing developers to use separate environments for building and running an application within a single Dockerfile. Each stage starts with its own isolated filesystem via a new FROM instruction, and only selected files are copied into the final image using COPY --from. A Go application that produced an 823MB single-stage image can be reduced to around 11MB by compiling in a builder stage and copying only the binary into a minimal base image like FROM scratch. For applications requiring SSL certificates or basic runtime libraries, options like Google's distroless images offer a middle ground between a bare binary and a full operating system.