API Bundle Size Limit

DevOps & Security

api-bundle-size-limit

API Bundle Size Limit is an Agent Skill for devops & security published in the webiny/webiny-js repository on GitHub: a SKILL.md instruction file an AI agent can load to do this task.

Covers how to configure the maximum allowed size of the Webiny API Lambda bundle using the Infra.Api.MaxBundleSize extension in webiny.config.tsx. Use when a project's API bundle exceeds the default 4.5 MB limit or when you want to enforce a stricter limit. Handles the extension syntax, byte calculations, and interpreting the build error message.

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API Bundle Size Limit

TL;DR

The Infra.Api.MaxBundleSize extension enforces a maximum size on the built API Lambda bundle. The default limit is 4.5 MB. If the bundle exceeds the limit the build fails with a clear error; add the extension to webiny.config.tsx to raise (or lower) it.

Default Behavior

By default Webiny enforces a 4.5 MB limit on the API Lambda bundle (handler.mjs). If the built output exceeds this, the build fails:

error   Build errors:
× asset size limit: The following asset(s) exceed the recommended size limit (4.5 MiB).
× entrypoint size limit: The following entrypoint(s) combined asset size exceeds the recommended limit (4.5 MiB).
error   build failed

Raising the Limit

Add Infra.Api.MaxBundleSize to webiny.config.tsx with size in bytes:

// webiny.config.tsx
import { Infra } from "webiny/extensions";

export const Extensions = () => (
  <>
    {/* Raise the API bundle size limit to 6 MB */}
    <Infra.Api.MaxBundleSize size={6 * 1024 * 1024} />
  </>
);

Common byte values:

MB	Bytes expression	Exact bytes
4.5	`Math.round(4.5 * 1024 * 1024)`	4718592 (default)
5	`5 * 1024 * 1024`	5242880
6	`6 * 1024 * 1024`	6291456
8	`8 * 1024 * 1024`	8388608
10	`10 * 1024 * 1024`	10485760

How It Works

The extension sets the WEBINY_INFRA_API_MAX_BUNDLE_SIZE environment variable (in bytes) which is read by the API bundler (@webiny/build-tools) at build time. The WEBINY_INFRA_ prefix ensures the variable is not automatically forwarded to the Lambda function's runtime environment.

Lowering the Limit

You can also enforce a stricter limit to catch bundle regressions early:

{
  /* Enforce a strict 3 MB limit */
}
<Infra.Api.MaxBundleSize size={3 * 1024 * 1024} />;

Quick Reference

Task	Snippet
Raise to 6 MB	`<Infra.Api.MaxBundleSize size={6 * 1024 * 1024} />`
Raise to 10 MB	`<Infra.Api.MaxBundleSize size={10 * 1024 * 1024} />`
Restore default (4.5 MB)	Remove the extension
Convert MB to bytes	`Math.round(N * 1024 * 1024)`

Related Skills

infra-env-var -- setting arbitrary environment variables in the project context
api-lambda-function -- adding custom Lambda functions to the API