Resend Python SDK on AWS Lambda: package the SDK and map ResendError to a 500

TL;DR

Install it into the deployment package (pip install into the bundle directory) or the import fails at cold start. - Set resend.api\_key at module scope from os.environ so warm invocations reuse it. Never hardcode the key in the handler file. - Catch ResendError and return a status code.

import os
import resend
from resend.exceptions import ResendError

resend.api_key [your value]

def handler(event, context):
    params = {
        "from": "[SENDER]",
        "to": ["[RECIPIENT]"],
        "subject": "hello world",
        "html": "<strong>it works!</strong>",
    }
    try:
        email = resend.Emails.send(params)
        return {"statusCode": 200, "body": str(email)}
    except ResendError as error:
        print(error)
        return {"statusCode": 502, "body": "email provider error"}

Steps

1. • resend is not in the Lambda Python runtime. Install it into the deployment

   package (pip install into the bundle directory) or the import fails at cold start.

• Set resend.api_key at module scope from os.environ so warm invocations reuse it. Never hardcode the key in the handler file.

• Catch ResendError and return a status code. An uncaught exception is a 502 with no useful signal; mapping it yourself keeps the failure legible.

• Do not return the raw exception to the caller. Log it, return a short error.

When to use

You are seeing this: Never hardcode the key in the handler file. - Catch ResendError and return a status code. Use this skill when you run into "Resend Python SDK on AWS Lambda: package the SDK and map ResendError to a 500".

When not to use

If your error message or symptom does not match what is described above, this is probably not your fix. Search for your exact error text instead of forcing this one to fit.

Versions

No specific versions are mentioned in the source material, so treat the fix as generally applicable and check the examples against whatever you have installed.

Why this happens

The original report does not dig into a root cause. It documents the symptom and the fix that resolved it.

The Python SDK's module-level api_key, resend.Emails.send, and ResendError are documented at https://resend.com/docs/send-with-python. The Lambda handler and environment-variable pattern follow the Lambda guide at https://resend.com/docs/send-with-aws-lambda.