Datadog Lambda Extension (Rust)

Datadog's AWS Lambda extension has been re-architected in Rust to significantly improve performance and reduce overhead. This rewrite cut cold starts by 82%, reduced memory usage by 40%, and shrunk the binary size from 55 MB to 7 MB. The new extension operates as a sidecar process, collecting and relaying telemetry data asynchronously. It supports flexible flush strategies (end of invocation, race the invocation, periodically) to balance telemetry immediacy with minimal overhead. The design constraints focused on minimizing impact on the Lambda function handler and post-runtime duration, leading to tradeoffs like manually writing AWS API calls instead of using SDKs.