I'm dealing with a frustrating issue with my Node.js AWS Lambda function that uses the @aws-sdk/client-dynamodb package. Whenever the function has been idle, the first DynamoDB read after a cold start takes way too long, usually between 800ms to over 2 seconds. It's clear that the delay isn't due to DynamoDB itself but rather from the overhead of various processes like Lambda spin-up, the Node.js runtime starting, and the SDK loading. My function is pretty lean—only includes this SDK and a few helper functions—but it really hits performance when cold. When warmed up, everything runs smoothly under 120ms. I'm currently keeping it warm with a ping every 5 minutes, but I'm wondering if there's a more efficient solution? Provisioned concurrency feels too pricey for my low-traffic usage, and SnapStart isn't available for Node.js at this time. How can I optimize this cold start phase?
4 Answers
Cold starts for Node.js Lambdas can add about 500ms in delay. One thing that could help is tree shaking, which can reduce the amount of code that needs to load during the start. Also, if you're up for using something experimental, take a look at AWS's low latency runtime they're working on.
Have you considered where you're initializing the DynamoDB client? If it's being created inside the handler function, that could be causing extra delay. Try to declare it at the top level of your file. Also, tools like Lambda Power Tuner can help you optimize performance.
Tree shaking is indeed a good call! Make sure you're not importing the entire SDK when you only need parts of it. You might also want to check your memory settings. Increasing your Lambda to about 1769 MB can give you an extra vCPU and could help with faster cold starts. Disabling TLS in the client could also be an option, but just for that first request to save time.
DynamoDB's use of RSA for key exchanges does add a bit of extra latency. If you haven't yet, you could try sending a request to DynamoDB during the initialization phase when the CPU has more resources available. It might help alleviate some of that initial hit.
Related Questions
How To: Running Codex CLI on Windows with Azure OpenAI
Set Wordpress Featured Image Using Javascript
How To Fix PHP Random Being The Same
Why no WebP Support with Wordpress
Replace Wordpress Cron With Linux Cron
Customize Yoast Canonical URL Programmatically