Maintenance: initialize AWS SDK client only when needed to improve performance in Parameters

[marcioemiranda]

Summary

Hello,
I am currently doing some performance tuning in our lambda functions and i notice that getting SSM parameters introduce some latency in the first execution. I've executed tests using both the getParameter utility and also SSMProvider. These were my findings:
ssm client instantiation: ~50ms
ssm provider instantiation: ~50ms
getParameter: 380ms (discounting 300ms from SDK, ~80ms)
SSM SDK get parameter: 300ms

In my tests I've used lambda functions configured with provisioned concurrency, so I tried to bring some of the latency to the INIT phase. I understand the best way to do it would be to:

1. Instantiante the SSM client in the static scope, maybe using a capture to trace this call
2. Passing the client to SSMProvider
3. Using SSMProvider instead of getParameter utility, which would add the latency of instantiating a SSM client inside the handler code.

However, I haven't noticed any gain of doing that. By inspecting the code bellow, I've noticed that SSM client is instantiated even when it's not used, i.e., when one passes the client as parameter. I believe this section could be optimized so that SSM client is only instantiated if none is available:

/**
   * It initializes the SSMProvider class.
   *
   * @param {SSMProviderOptions} config - The configuration object.
   */
  public constructor(config?: SSMProviderOptions) {
    super();

    this.client = new SSMClient(config?.clientConfig || {});
    if (config?.awsSdkV3Client) {
      if (isSdkClient(config.awsSdkV3Client)) {
        this.client = config.awsSdkV3Client;
      } else {
        console.warn(
          'awsSdkV3Client is not an AWS SDK v3 client, using default client'
        );
      }
    }
    addUserAgentMiddleware(this.client, 'parameters');
  }

Why is this needed?

Improve performance of first execution when SSMProvider has a SSM client.

Which area does this relate to?

Parameters

Solution

Instantiate SSM client only when none is available

Acknowledgment

• This request meets Powertools for AWS Lambda (TypeScript) Tenets
• Should this be considered in other Powertools for AWS Lambda languages? i.e. Python, Java, and .NET

Future readers

Please react with 👍 and your use case to help us understand customer demand.

[boring-cyborg]

Thanks for opening your first issue here! We'll come back to you as soon as we can.
In the meantime, check out the #typescript channel on our Powertools for AWS Lambda Discord: Invite link

[dreamorosi]

Hi @marcioemiranda, thank you for opening this issue.

You are right, the portion of the code that you highlighted could be refactored to create the client only when strictly needed. I'll put this item on the backlog and mark it as open for contributions.

On a side note, we are currently working on supporting ES Modules and will release support in the coming weeks. Once that's released you will be able to use top-level await and fetch the secrets outside of the Lambda handler as described in this post.

[marcioemiranda]

@dreamorosi this is excelent news, will have big impact in performance