Performance Issue: Server Restarts on Every Invocation

[cjnoname]

Hi,

We're encountering a performance issue with this setup. It seems the server restarts every time the following command is executed:

return await stdioServerAdapter(serverParams, event, context);

This triggers all the server startup scripts inside the ./mcp-server.js file, including database connections, secret fetching, and other initialization logic.

Is there a recommended way to cache the server instance so that it starts only once and stays in memory for future invocations?

Thanks!

[clareliguori]

If it's safe to re-use your MCP server process across users, then you could try instantiating the server adapter outside of the handler function as a global variable. I have never tried this with child processes, but it does work for database connections. For example:
https://www.jeremydaly.com/reuse-database-connections-aws-lambda/

I'm not sure how the MCP server child process will behave after being "frozen" and "thawed" in the Lambda execution environment.

To try this, you'd need to fork stdioServerAdapter.ts and move creating and connecting to the transport to a global variable:
https://github.com/awslabs/run-model-context-protocol-servers-with-aws-lambda/blob/main/src/typescript/src/server-adapter/stdioServerAdapter.ts#L117-L119

[cjnoname]

If it's safe to re-use your MCP server process across users, then you could try instantiating the server adapter outside of the handler function as a global variable. I have never tried this with child processes, but it does work for database connections. For example: https://www.jeremydaly.com/reuse-database-connections-aws-lambda/

I'm not sure how the MCP server child process will behave after being "frozen" and "thawed" in the Lambda execution environment.

To try this, you'd need to fork stdioServerAdapter.ts and move creating and connecting to the transport to a global variable: https://github.com/awslabs/run-model-context-protocol-servers-with-aws-lambda/blob/main/src/typescript/src/server-adapter/stdioServerAdapter.ts#L117-L119

Thanks so much for your quick reply — I tried it, and it works like a charm!

Just one more question: what's the easiest way to view logs from the MCP server? I used console.log, but I can't see any logs in CloudWatch.

[clareliguori]

If it's an MCP server you own, logs need to go to stderr because stdio-based MCP servers use stdout for communication between parent and child process.

You can do something like:

const { Console } = require("console");
const consoleLogger = new Console(process.stderr);
consoleLogger.log("hello world");

[cjnoname]

If it's an MCP server you own, logs need to go to stderr because stdio-based MCP servers use stdout for communication between parent and child process.

You can do something like:

const { Console } = require("console");
const consoleLogger = new Console(process.stderr);
consoleLogger.log("hello world");

Man, you are a legend! Thank you so much for your help!