Editing Docker (section)

== <span style="color: #FFFFFF;">Analyzing</span> ==
'''Image size matters.''' Large images take longer to push, pull, and start. Common sources of bloat:
* Using a full OS base image (ubuntu:latest ~80MB) instead of a slim or Alpine variant (~5MB)
* Build tools (compilers, dev dependencies) left in the final image
* File copies that include unnecessary files (.git, node_modules on Node, __pycache__ on Python)

'''Multi-stage builds''' solve the build-tools problem: use one stage with a full build environment, then copy only the compiled artifact into a minimal final stage.

:<code>FROM golang:1.22 AS builder
WORKDIR /app
COPY . .
RUN go build -o server .

FROM alpine:3.19
COPY --from=builder /app/server /server
CMD ["/server"]</code>

The final image contains only Alpine and the compiled binary � no Go toolchain.

'''Layer cache invalidation''' is a common performance trap. Copying the full source before installing dependencies means any code change invalidates the dependency install layer. Always copy dependency manifests first, install, then copy source code.

'''Container statefulness''': containers are designed to be ephemeral. Any data written inside a container's writable layer is lost when the container is removed. Databases, uploaded files, and anything that must persist must use volumes or external storage.

'''Networking modes''': containers on the same Docker network can reach each other by service name. Containers on different networks cannot see each other by default. The default bridge network does not provide DNS resolution between containers � use a named network with Compose or explicit network creation.
</div>

<div style="background-color: #483D8B; color: #FFFFFF; padding: 20px; border-radius: 8px; margin-bottom: 15px;">