Launched in October 2026, Web Functions run a normal HTTP server on Lambda: no adapter, many concurrent requests per environment, native streaming, and billing on requests, active vCPU and held memory. AWS's worked examples, how it compares with Event Functions and function URLs, and what to check before moving.
Running a web framework on Lambda used to mean an adapter that translated API Gateway or function URL events into HTTP requests, one request per environment, billed on wall-clock time. Web Functions remove all three constraints: your server listens on a port, an environment handles concurrent requests, and you pay for CPU only while code is running.
From the Lambda pricing page. Compute is billed at 1 ms granularity; memory is billed for as long as the environment runs, including between requests.
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Assumes one environment running all month and serving all traffic; excludes free tier and data transfer.
Runtime: Node.js at launch, on Arm. Check native dependencies have Arm builds.
Concurrency safety: module-level state is now shared by simultaneous requests, as on any server. Code written for one-request-per-environment Lambda can have bugs that only appear here.
Regions: launched in US East (N. Virginia, Ohio), US West (Oregon), Europe (Ireland) and Asia Pacific (Tokyo).
Idle cost: memory is billed while an environment runs, so a rarely used service may cost more than an Event Function that scales to zero between requests.
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Lambda Web Functions vs Event Functions: Where the New Model Saves Money, and Where It Doesn't
Web Functions bill active CPU and held memory; Event Functions bill wall-clock time multiplied by memory. For AWS's own three example workloads, classic Lambda at 512 MB is cheaper. Once requests spend seconds waiting (LLM streaming, slow APIs, long polls) Web Functions win by 40 times or more: a 10-second stream costs about $3 per million requests instead of $134. The arithmetic, the crossover and a checklist.
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AWS Lambda Is Five Things Now: Event Functions, Web Functions, Durable Functions, MicroVMs and Managed Instances
In twelve months Lambda grew from one compute model to five. Event Functions (the classic model, renamed), Web Functions for HTTP servers billed on active CPU, Durable Functions for long workflows, MicroVMs for isolated sandboxes, and Managed Instances on EC2. What each is for and how each bills.
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As of October 25, 2026. Provided as is, for general information, and accurate to the best of our knowledge on the date shown. Not legal, compliance, tax, financial or other professional advice. Prices, limits and vendor services change; check current vendor documentation before relying on anything here. Terms of use.