run npm install in here Don't analyze app.js before trying the task

Open app.js and modify HOW_OBVIOUS_THE_FLAME_GRAPH_SHOULD_BE_ON_SCALE_1_TO_100 It will affect how hard it is to find the function you're looking for.

Run the app through perf. Make the following request:

curl http://localhost:8080/api/tick

Or just open it in the browser.

Generate a flame graph, identify the function in your code that performs the long synchronous computation.

Now for something more realistic.

Start the app, open http://localhost:8080/ to simulate traffic (it repeatedly makes requests to /api/tick), run a short perf on the running process and generate a flame graph. See if you would identify the function under real traffic. Try with shorter sleep and lower profiling frequency too.