🧭 Scenario · Make the call
The login that breaks on the second click
The situation
A web app recently grew from one server to several behind a load balancer. Now users complain that they log in fine, but a click or two later they're suddenly logged out and asked to sign in again. Digging in, the team finds each server stores who's logged in inside its own memory — and the load balancer freely sends a user's next request to a different server, one that has never heard of them.
You haven't read about this exact system. That's the point — walk the three questions a designer asks: what's really wrong, what fixes it, and what does the fix cost?
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Diagnose
Read past the story. What's the REAL problem — not what the feature does, but what's actually going wrong?
Look past the story. What's the REAL problem here?