Announcing AWS Lambda Web Functions

Summary

• AWS Lambda Web Functions allow standard HTTP web applications to run on Lambda without rewriting code into event handlers.
• Developers can deploy standard port-listening servers built with Express, Hono, Fastify, Next.js, or any Node.js framework with a single command.
• Lambda automatically handles scaling, multi-region distribution, and active CPU billing for Web Functions.
• AWS Lambda now offers three form factors: Event Functions, Web Functions, and MicroVMs, all built on Firecracker isolation technology.
• Lambda Event Functions use an event-driven, single-concurrent handler model with wall-clock billing for processing events, queue consumption, and service invocations.
• Lambda Web Functions use an HTTP-native programming model with multi-concurrent execution and active CPU billing for web applications, API backends, and interactive HTTP workloads.
• Lambda MicroVMs provide isolated, stateful sandbox environments with customer-managed lifecycles for running untrusted or user-generated code.
• Each Web Function execution environment handles up to 128 concurrent requests simultaneously to share warm environments during traffic bursts.
• Web Functions meter CPU time for active processing while memory is metered for the duration the execution environment exists.
• Code for Web Functions requires no adapters or wrappers and only needs the AWS_LAMBDA_HTTP_ENDPOINT environment variable to listen on a port.
• The AWS CLI command "aws lambda-web deploy" bundles source code, creates the Web Function, publishes a revision, attaches an endpoint, and returns a live HTTPS URL.
• A revision is an immutable snapshot of deployed code, while an endpoint is an HTTPS URL that routes traffic to a revision or splits traffic across revisions.
• Deploying to multiple regions replicates code and configures latency-based routing automatically through a single global URL.
• Traffic can be shifted between revisions using an API call to enable canary deployments with specific weight distributions.
• Web Functions can serve as the origin for Amazon CloudFront distributions to combine CDN performance for static assets with serverless compute for dynamic content.
• CloudFront origin access control (OAC) can be attached to a Web Function endpoint to sign requests and restrict access to the distribution.
• AWS Lambda Web Functions are available in US East (N. Virginia), US East (Ohio), US West (Oregon), Asia Pacific (Tokyo), and Europe (Ireland).
• Web Functions run Node.js 24 (nodejs24.x) on Arm64 at launch and support Amazon Virtual Private Cloud (VPC) connectivity.