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: