[rburhum]

Put a database behind it with complicated enough requests, and you'll run out of connections to the db regardless if you have async io. You'll have to add a connection pooler or multiple master/slave dbs - and even then you will run into problems with enough traffic. Not everything is sending back some json from something that is readily available.

[SomeCallMeTim]

To really scale a complex architecture, certainly there are other things you need to do, like setting up database replication and/or sharding, caching, and other scaling strategies.

That can typically be done from Node by simply adding the "use pooling" option in your database library (or sometimes by switching to the NPM for that database that enables pooling), and when you have additional slave databases, adding those to the database init call.

As far as Node is concerned, it really is that easy. Scaling PHP, though, pretty much requires that you add more threads, which means (after a point) you need a lot of RAM, or just adding more instances and load balancing between them.

Node won't prevent database scaling issues, but it will keep the part that it does handle a lot easier to maintain.