What specific mechanism does Docker use during the image build process to speed up subsequent builds by reusing the results of unchanged steps from previous builds?

Docker uses a mechanism called layer caching to speed up subsequent image builds. A Docker image is composed of read-only layers, where each instruction in a Dockerfile creates a new layer. When Docker builds an image, it processes the Dockerfile instructions sequentially from top to bottom. For each instruction, Docker first checks if it has a cached layer that corresponds to that exact instruction from a previous build. This check involves comparing the instruction itself and, more importantly, a checksum of any files or data involved in that step. For ex....