Design a shipped feature so it actually gets used — lower the cost of starting, give one obvious next step, and plan for the moment the user stalls, is embarrassed, is in the wrong place, or gets it wrong. Draws the pattern library from Duolingo's public…
Run LLM agents as production infrastructure instead of demos — split what an agent is (prompt, tools, access, output schema) from how it runs (runtime, model, SDK, environment), make every step durable and retryable, grade the diff instead of the prose, cap…
Decide where to point AI so it changes your cost structure instead of adding a feature — which bottleneck absorbs the automation budget, how to divide labor between expert staff and models, when to adopt a capability that is still visibly bad, and how to make…
Treat working memory as the binding constraint on every screen, session, and document — cap what competes for it, cut what wastes it, and deliberately spend what is left on the one thing you are trying to teach. Covers how much new material fits in one unit,…
Make a server request fast and hard to break, using Duolingo's published engineering results as the case study. Covers what to delete from the synchronous request path, how to split data into precompute-and-cache versus caller-injected, how long to hold a…
Duolingo's playbook for picking and entering a new market or adding a second product line — where to attack an incumbent, what to port from the product that already works, and what to rebuild from a blank page. Use when someone asks "should we enter this…
Build a reusable cast, illustration style, animation vocabulary and avatar system that a small team can actually produce at volume, and make those assets do product work instead of decorating it. Covers choosing a visual style by production throughput,…
Build the team the way Duolingo built theirs — the Green Machine operating model, talent density over headcount, candor protocol ("focus on what, not who"), hire-slow / fire-fast, and the "no process unless it makes decisions better" rule. Use when the user…
