Cut Your Docker Build Time in Half: 6 Essential Optimization Techniques

"Docker builds images in layers, caching each one.When you rebuild, Docker reuses unchanged layers to avoid re-executing steps - this is build caching. So the order of your instructions and the size of your build context have huge impact on speed and image size. Here are the quick tips to optimize and achieve 2 times faster speed building images:"

"Every instruction ( FROM, RUN, COPY, etc.) creates a new layer.When one layer changes, all layers after it are rebuilt.So to maximize cache reuse, put the least frequently changing instructions (e.g., installing OS packages) near the top, and the most frequently changing (like copying your source code) at the bottom."

"Example: Bad Dockerfile: When you change any source file, the entire build re-runs from COPY . ., which invalidates cache for npm install."

Docker builds images in layers and caches each layer so rebuilds can reuse unchanged layers instead of re-executing steps. Build caching depends on instruction order and build context size, both affecting build speed and image size. Each Dockerfile instruction (FROM, RUN, COPY, etc.) creates a new layer. When any layer changes, all subsequent layers are rebuilt. To maximize cache reuse, place least-frequently changing steps like OS package installation near the top and put frequent changes such as copying source code toward the bottom to avoid invalidating earlier caches like npm install.

Read at Medium