I recently watched an by Matt Lavin on optimization tips for Lambda and saw a slide on making DynamoDB use HTTP keep-alive. It reminded me of a conversation I had with , so I set out to test the effect this simple optimization has. excellent talk Sebastian Cohnen What is it all about? As it turns out, Node.js’s default HTTP agent doesn’t use keep-alive and therefore every request would incur the cost of setting up a new TCP connection. This is clearly inefficient, as you need to perform a to establish a TCP connection. For operations that are short-lived (such as DynamoDB operations, which typically complete within a single digit ms) the latency overhead of establishing the TCP connection might be greater than the operation itself. three-way handshake With the Node.js AWS SDK, you can to use for ALL clients with just a few lines of code. You can also override the settings for individual clients too. override the HTTP agent The tests To test the effect of enabling HTTP keep-alive, I setup a simple Lambda function behind API Gateway. Essentially this function puts an item into a DynamoDB Table, and that’s it. For this experiment, I wanted to see how well the HTTP keep-alive fared across multiple invocations and how much of a difference do we see with this simple change. The results Without HTTP keep-alive, the DynamoDB operation averaged around . 33ms With HTTP keep-alive, that average drops to around . 10ms As we suspected, the overhead (33ms-10ms = 23ms) was greater than the cost of the operation itself. The experiment shows that the connection is reused across multiple invocations just fine. With a very simple change, we were able to improve execution time by ~20ms, or to put it more impressively, reduce response time by 70%. That’s good return on investment in my book, but the difference is still not noticeable to the human eye. But what if we scale this to 10 sequential DynamoDB operations in a single function? With HTTP keep-alive, the function’s execution time averages around . 60ms Without HTTP keep-alive, the average execution time rises to . 180ms As I curl the endpoint, the difference of is definitely noticeable. This difference can start to impact user experience, and as Amazon found 10 years ago, . 120ms adding 100ms of latency can reduce sales by as much as 1% Like what you’re reading, why not check out my with Manning or ? video course hire me In the video course we will cover topics including: authentication & authorization with API Gateway & Cognito testing & running functions locally CI/CD log aggregation monitoring best practices distributed tracing with X-Ray tracking correlation IDs performance & cost optimization error handling config management canary deployment VPC security leading practices for Lambda, Kinesis, and API Gateway You can also get the face price with the code . Hurry though, this discount is only available while we’re in Manning’s Early Access Program (MEAP). 40% off ytcui

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