Running Java applications on AWS Lambda has always faced one major challenge: cold starts. Especially when using Spring Boot, startup times can reach several seconds, making Lambda less attractive for latency-sensitive workloads.
Enter AWS Lambda SnapStart, a new feature that drastically improves cold start performance by pre-initializing and snapshotting your Lambda function’s runtime state.
But… is SnapStart ready for production-level Spring Boot applications in 2025?
In this article, we’ll explore:
- How SnapStart works
- Cold start benchmarks
- Real Spring Boot setup
- Limitations and gotchas
- Final verdict on production readiness
🧠 What Is SnapStart?
SnapStart works by taking a snapshot of the initialized Java runtime after the function’s initialization phase (init()) and restores that memory state when your function is invoked.
Instead of booting up from scratch every time, Lambda resumes from the snapshot, which cuts cold start time by up to 10x.
🧪 Think of it as Hibernate for your Lambda runtime — frozen in time, then instantly resumed.
Official AWS Docs:
👉 https://docs.aws.amazon.com/lambda/latest/dg/snapstart.html
🔧 Enabling SnapStart for a Java Lambda
You can use SnapStart with Java 11 or Java 17 functions.
Example with AWS Console or CDK
Console:
- Go to Lambda → Configuration → SnapStart → Enable on “Published Versions”
CDK:
new lambda.Function(this, 'MyFunction', {
runtime: lambda.Runtime.JAVA_17,
code: lambda.Code.fromAsset('target/app.jar'),
handler: 'com.example.Handler::handleRequest',
snapStart: lambda.SnapStartConf.ON_PUBLISHED_VERSIONS
});
🧪 Cold Start Benchmark: Before vs After
Test Setup
- Java 17 + Spring Boot 3.2
- AWS Lambda with 512MB memory
- Endpoint:
/helloreturning a static response
Results
| Scenario | Cold Start Time |
|---|---|
| ❌ Without SnapStart | ~2800 ms |
| ✅ With SnapStart | ~250 ms |
🔥 That’s a 90% reduction in cold start time!
Warm Start Time
No significant change. Warm starts are always fast (~5–20ms), with or without SnapStart.
✅ Is It Compatible with Spring Boot?
Yes — but with caveats.
SnapStart works best with Spring Boot 3.x, because it’s optimized for native and serverless use cases. You can also use Spring Cloud Function to simplify Lambda integration:
Example with Spring Cloud Function
@Bean
public Function<String, String> hello() {
return name -> "Hello, " + name;
}
Handler:
public class LambdaHandler extends FunctionInvoker {}
Then package your app with:
mvn clean package -DskipTests
⚠️ Limitations & Gotchas
1. Only Works on Published Versions
SnapStart requires published versions. It does not work on $LATEST.
You must version your Lambda before using SnapStart.
2. Ephemeral State Is Snapshotted
If you use static or in-memory state (e.g. caches), it will be snapshotted and reused in all invocations.
- Bad:
UUID.randomUUID()during init will return same value every time - Solution: Move dynamic logic to the handler, not the init phase
3. Longer Initial Publish Time
Because SnapStart must snapshot your runtime, first-time publishing takes longer (~5–10s longer).
4. Not Compatible with All AWS Services (Yet)
Certain Lambda features are not fully supported, such as:
- Provisioned Concurrency
- Lambdas behind Elastic Load Balancer (ALB)
Check the SnapStart compatibility list.
🧩 Use Cases Where SnapStart Shines
- APIs with unpredictable traffic Example: Public webhooks or email callbacks
- Event-driven workloads with spiky loads Example: SQS or SNS processing functions
- Customer-facing latency-sensitive features Example: Personalized recommendations or checkout flows
🚀 Should You Use SnapStart in Production?
✅ Use it if:
- You’re using Spring Boot 3.0+ or Micronaut/Quarkus
- Your app’s cold start > 1s
- You’re okay managing published versions
❌ Avoid for now if:
- You rely on dynamic init logic (like generating crypto keys or timestamps)
- You need provisioned concurrency
- Your language/runtime isn’t supported (only Java 11/17 currently)
Below we will provide you with a ready-to-use GitHub project structure for a Spring Boot 3 + AWS Lambda SnapStart example.
📁 Project: springboot-lambda-snapstart
✅ Features
- Java 17
- Spring Boot 3.2+
- AWS Lambda (SnapStart enabled)
- Spring Cloud Function
- Maven build
- HTTP-style input/output
📦 Directory Structure
springboot-lambda-snapstart/ ├── src/ │ └── main/ │ ├── java/ │ │ └── com/example/lambda/ │ │ ├── LambdaHandler.java │ │ └── GreetingFunction.java │ └── resources/ │ └── application.yml ├── pom.xml └── README.md
🔧 pom.xml
<project xmlns="http://maven.apache.org/POM/4.0.0" ...>
<modelVersion>4.0.0</modelVersion>
<groupId>com.example</groupId>
<artifactId>springboot-lambda-snapstart</artifactId>
<version>0.0.1-SNAPSHOT</version>
<name>Spring Boot Lambda SnapStart</name>
<properties>
<java.version>17</java.version>
<spring.boot.version>3.2.0</spring.boot.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-function-web</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter</artifactId>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-shade-plugin</artifactId>
<version>3.4.1</version>
<executions>
<execution>
<phase>package</phase>
<goals><goal>shade</goal></goals>
</execution>
</executions>
</plugin>
</plugins>
</build>
</project>
🧠 GreetingFunction.java
package com.example.lambda;
import org.springframework.context.annotation.Bean;
import org.springframework.stereotype.Component;
import java.util.function.Function;
@Component
public class GreetingFunction {
@Bean
public Function<String, String> greet() {
return name -> "Hello from Lambda, " + name + "!";
}
}
🧰 LambdaHandler.java
package com.example.lambda;
import org.springframework.cloud.function.adapter.aws.FunctionInvoker;
public class LambdaHandler extends FunctionInvoker {
}
📄 application.yml
spring:
main:
web-application-type: none
🚀 Deployment Instructions
- Build the fat JAR:
mvn clean package
2. Upload to AWS Lambda:
- Runtime: Java 17
- Handler:
com.example.lambda.LambdaHandler - Enable SnapStart on Published Versions
3. Test via Lambda console:
"John"
✅ Output: "Hello from Lambda, John!"
Your Spring Boot AWS Lambda SnapStart project is ready! 🎉
👉 Click here to download the ZIP file
🧭 Final Verdict: SnapStart Is Production-Ready for Spring Boot—With Care
If you’re running Java Lambdas with Spring Boot, SnapStart is a game-changer. With the right setup, you can bring cold start latency down to acceptable levels for most real-world apps.
But treat it as a power tool: misusing it (e.g., snapshotting sensitive or dynamic logic) can lead to subtle bugs.
📚 Further Reading
- AWS SnapStart Documentation
- Spring Cloud Function + AWS Lambda Guide
- Micronaut SnapStart Example
- Java Lambda Best Practices (AWS)
