Day 56 drills

Paper first. Plan the slice before you type.

D1 (the walking skeleton: the thinnest end-to-end path through your slice, one request, one thing it does, one response):

D2 (persistence: what really stores your data, why not a dict, and what happens on restart):

D3 (metrics: the three or four numbers your /metrics endpoint exposes for your system to be observable):

D4 (the predicted bottleneck: where you think your slice will cap out under load, and why, written before you build):

D5 (read app.py: find the deliberate bottleneck, and say in one sentence why it serialises the service no matter how many clients hit it):