Node.js in Flame Graphs

The word you want is "lessons".

> ...also saw that the process’s heap size stayed fairly constant at around 1.2 Gb.

This is because 1.2 GB is the max allowed heap size in v8. Increasing beyond this value has no effect.

> ...It’s unclear why Express.js chose not to use a constant time data structure like a map to store its handlers.

It it is non-trivial (not possible?) to do this in O(1) for routes that use matching / wildcards, etc. This optimization would only be possible for simple routes.

The word you want is "lessons".

Jeez, not only is your comment offtopic and pedantic, it's also wrong.

I believe the word you want is "incorrect."

/sarcasm

Its actually quite clear - most routes are defined by a regex rather than a string, so there is no built-in structure (if there's a way at all) to do O(1) lookups in the routing table. A router that only allowed string route definitions would be faster but far less useful.

I can't explain away the recursion, though. That seems wholly unnecessary.

Edit: Actually, I figured that out, too. You can put middleware in a router so it only runs on certain URL patterns. The only difference between a normal route handler and a middleware function is that a middleware function uses the third argument (an optional callback) and calls it when done to allow the route matcher to continue through the routes array. This can be asynchronous (thus the callback), so the router has to recurse through the routes array instead of looping.