AWS SDK for Java 2.x Introduces Client Warm-Up to Reduce Cold Starts

The new SDK client warm-up feature addresses cold-start latency in AWS SDK for Java 2.x applications, which typically experience slower first service calls. It pre-exercises the SDK request path during application startup, improving subsequent call performance.

Developers can invoke `SdkWarmUp.warmUp()` without arguments during application startup to initialize every service client found on the application's classpath along with their corresponding HTTP clients.

For finer control, the `warmUp(Class... clients)` overload allows developers to specify which synchronous or asynchronous client classes to warm, preventing unnecessary warm-up of unused service modules and reducing startup time.

The warm-up feature can be integrated into AWS Lambda functions that use SnapStart by calling `SdkWarmUp.warmUp()` in the function handler's constructor. This ensures clients are warm within the snapshot, benefiting every invocation after a restore.

The warm-up feature loads JVM classes and compiles JIT code for the SDK request path, and establishes network connections by making an unsigned, no-credential network call to an AWS endpoint. This process avoids cold start overheads on the first actual service interaction.

The SDK client warm-up feature is available in Java SDK version 2.54.0 and later, shipping as part of the `sdk-core` module without requiring additional dependencies.