Guess the stack. Learn why it works.
Five questions a round, getting harder as you climb — "what does this real product actually run on, and why." After each round you choose: bank your points, or gamble them on a harder one. Every answer comes with the engineering reasoning behind it.
How a round works
A correct answer in round 7 is worth seven points, so climbing pays. But score fewer than two out of five in a round and you lose everything you were holding — knowing when to stop is half the game. No account needed, just a nickname for the board.
Easy
Well-known, widely reported choices — the kind of fact that shows up in any "how X was built" write-up.
Medium
Still documented, but more specific — a migration, a framework swap, a deliberate trade-off.
Hard
Infrastructure-level detail: the database, the queue, the in-house tool built to solve one particular problem.
From the stack directory
Short profiles of what real companies run, and why.
Slack
Slack was originally built primarily in PHP, and as it scaled the team began migrating performance-sensitive parts of t…
Dropbox
Dropbox leaned heavily on Python across its backend and desktop client for years, later rewriting performance-critical …
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