AWS: Read Timeout when Invoking Lambda

 I have an AWS Lambda that invokes another Lambda synchronously. Nothing was wrong with it until recently, when the other Lambda started performing more tasks and taking more time. Suddenly, the caller Lambda started failing with this weird message:

ReadTimeoutError: Read timeout on endpoint URL: "https://lambda.eu-central-1.amazonaws.com/2015-03-31/functions/MyOtherLambda/invocations"

Looking at the logs of my other Lambda, I could see that it ran fine, although it was executed several times. After some research on the Internet, I found this article from AWS support that explains that when invoking a Lambda synchronously, there is a default timeout of 60 seconds, and 3 retries. This can be configured when creating the client.

In Python using boto3 for instance, you have to use the Config object:

import boto3

from botocore.config import Config

lambda_client = boto3.client("lambda", config=Config(read_timeout=600))

Now, my invoked lambda has 10 minutes to perform its tasks.