Bot replies twice when Lambda cold starts

Description

I have setup a Slack Bolt on AWS Lambda by following this instruction - https://slack.dev/bolt-js/deployments/aws-lambda#set-up-aws-lambda

I want the Bot to reply ‘hi’ if someone says ‘help’. Sample code:

app.message('help', async ({ message, say }) => {
  await say(`hi`);
});

I noticed that whenever the Lambda is cold, the Bot always says hi twice. But when Lambda is warm, the Bot only replies once. What is the possible solution to prevent the Bot from answering it twice when Lambda cold starts. Thanks!

What type of issue is this? (place an x in one of the [ ])

• bug
• enhancement (feature request)
• question
• documentation related
• example code related
• testing related
• discussion

Requirements (place an x in each of the [ ])

• I’ve read and understood the Contributing guidelines and have done my best effort to follow them.
• I’ve read and agree to the Code of Conduct.
• I’ve searched for any related issues and avoided creating a duplicate issue.

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Bug Report

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Reproducible in:

package version:

        "@slack/bolt": "^3.2.0",
        "@vendia/serverless-express": "^4.3.3",

node version: v12.14.1

Environment: AWS Lambda

[seratch]

@jc1518 Yes, your idea sounds a great approach to me 👍

[jc1518]

Hi @mwbrooks ,

Thanks for the quick response. Yes, I have the processBeforeResponse: true settings. I am thinking this issue could be caused by the Lambda concurrent execution? When Lambda cold starts, it may trigger more than one execution.