AWS Announces Lambda Web Functions for Standard HTTP Applications

Amazon Web Services has announced AWS Lambda Web Functions, a new form factor that lets developers run standard HTTP web applications on Lambda without rewriting their code into an event handler. Applications built with Express, Hono, Fastify, Next.js, or any Node.js framework can be deployed with a single command, while Lambda handles scaling, multi-region distribution, and active CPU billing.

Three Lambda Form Factors

With this launch, AWS Lambda now offers three distinct form factors, each built on the same Firecracker isolation technology. Lambda Event Functions use the event-driven, single-concurrent handler model with wall-clock billing and suit event processing, queue consumers, and invocations triggered by other AWS services. Lambda Web Functions use an HTTP-native programming model with multi-concurrent execution and active CPU billing, targeting 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.

How Web Functions Work

Each Web Function execution environment handles up to 128 concurrent requests simultaneously, so bursts of traffic can share warm environments instead of mapping each request to a new one. Web Functions meter the CPU time the code actually uses, meaning time spent waiting on a database query or an API call consumes little CPU, while memory is metered for as long as the execution environment exists. AWS says this can reduce compute costs for I/O-heavy workloads such as server-side rendering, API backends, and AI inference endpoints streaming token responses.

Developers write a standard port-listening server and read the host and port from the AWS_LAMBDA_HTTP_ENDPOINT environment variable that Lambda sets automatically. Deployment happens through the AWS CLI with a single command, aws lambda-web deploy, which bundles the source, creates the Web Function, publishes its first revision, attaches an endpoint, and returns a live HTTPS URL. Revisions are immutable snapshots of deployed code, and endpoints are HTTPS URLs that route traffic to a revision or split traffic across revisions.

Multi-Region Deployments and Traffic Shifting

Passing a --regions flag to the deploy command replicates the code to multiple regions and configures latency-based routing automatically through one global URL, routing each request to the region with the lowest latency for the caller on a best-effort basis. Re-running the deploy command after a code change uploads a new revision and points the endpoint at it within seconds. For gradual rollouts, a single API call can shift traffic between revisions with configured weights, enabling canary deployments without additional tooling.

CloudFront Integration and Availability

Web Functions can serve as an origin for Amazon CloudFront distributions, with static assets served from cache and dynamic requests routed to the function. The launch also improves the private-origin experience: customers attach CloudFront origin access control to a Web Function endpoint, so CloudFront signs requests and the endpoint allows only that distribution to invoke it, matching the private-origin pattern CloudFront already provides for Amazon S3.

Lambda Web Functions is available today 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 VPC connectivity for accessing resources inside a VPC.

Sources: AWS News Blog