Multi-stage Docker builds in Spring Boot - Performance & Optimization

Performance: Multi-stage Docker builds

HIGH IMPACT

This affects page load speed by reducing container image size and startup time, improving deployment speed and runtime performance.

Building a Spring Boot app Docker image efficiently

Spring Boot

FROM maven:3.9.0-eclipse-temurin-17 AS build
COPY pom.xml /app/
COPY src /app/src/
WORKDIR /app
RUN mvn clean package -DskipTests

FROM eclipse-temurin:17-jre
COPY --from=build /app/target/*.jar /app/app.jar
CMD ["java", "-jar", "/app/app.jar"]

Build tools and source code stay in the build stage only; final image contains just the runnable jar and JRE.

📈 Performance GainReduces image size by 80-90%, speeds up container startup and deployment

Building a Spring Boot app Docker image efficiently

Spring Boot

FROM openjdk:17
COPY . /app
WORKDIR /app
RUN ./mvnw package
CMD ["java", "-jar", "target/app.jar"]

This copies all source files and build tools into the final image, making it large and slow to load.

📉 Performance CostAdds 500+ MB to image size, increasing container startup time and network transfer delays

Performance Comparison

Pattern	Image Size	Build Time	Startup Time	Verdict
Single-stage build with full source	Large (500+ MB)	Long (includes build tools)	Slow (large image load)	[X] Bad
Multi-stage build with separate build/runtime	Small (50-100 MB)	Moderate (build stage only)	Fast (small image load)	[OK] Good

Rendering Pipeline

Multi-stage builds reduce the container image size, which speeds up image download and container startup, improving the time until the app is ready to serve content.

→Network Transfer

→Container Startup

→Application Load

⚠️ BottleneckNetwork Transfer and Container Startup time due to large image size

Core Web Vital Affected

LCP

This affects page load speed by reducing container image size and startup time, improving deployment speed and runtime performance.

Optimization Tips

1Keep build tools and source code out of the final image.

2Use separate stages for building and running your app.

3Smaller images load faster and reduce deployment time.

Performance Quiz - 3 Questions

What is the main performance benefit of using multi-stage Docker builds for a Spring Boot app?

A Smaller final image size leading to faster container startup

B Faster Maven build times inside the container

C Improved Java runtime performance inside the container

D Better logging and debugging capabilities

DevTools: Docker CLI and Container Runtime

How to check: Use 'docker images' to compare image sizes; use 'docker stats' and logs to check container startup time; use network tools to measure image download time.

What to look for: Smaller image size and faster container startup times indicate better performance with multi-stage builds.