It is a problem to maintain. Simple example: how do you remove sessions in a multi server environment? Well, you can set a config to do that at random which imposes a cost for that particular request. Or you can run a corn job. This is not a decision in most other scripting languages.

Don’t get me started on concurrency either...

This is a decision in all scripting languages.

PHP solves concurrency very well - it just passes the problem to the web server.

If you need multithreading to service a http request then you are either doing something wrong, or over-engineering the problem. Other language platforms also service requests in a single thread, including Node.

Node though multiplexes more than one request at a time to a single thread / process and no built in ability to clean up after itself.

Why is this not an issue in other scripting languages? You either delete at runtime or delete in a separate process. What other options are there?

It’s easy to maintain if you don’t change versions. If you upgrade, have fun finding all the pages throwing new warnings.

Contrast that with going up one major version in Scala where all I need to do is fix the compile errors and then I’m confident it won’t surprise me with runtime errors.