How to Cut Docker Image Size by 90% Using Lean Base Images and Multi-Stage Builds

Bloated Docker images often stem from base images like node:latest or python:3.11, which bundle full operating systems, compilers, and package managers that most applications never use. Developers can dramatically reduce image size by switching to minimal base images such as Alpine Linux (~5MB) or Google's Distroless images, which include only the runtime and necessary dependencies. Multi-stage builds allow teams to compile or install dependencies in one stage and copy only the final artifacts into a lean runtime image, shrinking Go app images to as little as 10–20MB. Additional gains come from combining RUN commands to reduce image layers, using flags like --no-cache-dir for pip and --only=production for npm, and configuring a .dockerignore file to exclude folders like node_modules and .git from the build context. Together, these techniques can reduce Docker image sizes by 90% or more without compromising application functionality.