Reusing connections with keep-alive in Node.js

The default Node.js HTTP/HTTPS agent creates a new TCP connection for every new request. To avoid the cost of establishing a new connection, the SDK for JavaScript reuses TCP connections.

For short-lived operations, such as Amazon DynamoDB queries, the latency overhead of setting up a TCP connection might be greater than the operation itself. Additionally, since DynamoDB encryption at rest is integrated with AWS KMS, you may experience latencies from the database having to re-establish new AWS KMS cache entries for each operation.

To disable reusing TCP connections, set the AWS_NODEJS_CONNECTION_REUSE_ENABLED environment variable to false (the default is true).

You can also disable keeping these connections alive on a per-service client basis, as shown in the following example for a DynamoDB client.

import { DynamoDBClient } from "@aws-sdk/client-dynamodb";
import { NodeHttpHandler } from "@smithy/node-http-handler";
import { Agent } from "http";
const dynamodbClient = new DynamoDBClient({
    requestHandler: new NodeHttpHandler({
        httpAgent: new Agent({ keepAlive: false })
    })
});

If keepAlive is enabled, you can also set the initial delay for TCP Keep-Alive packets with keepAliveMsecs, which by default is 1000 ms. See the Node.js documentation for details.