Working notes from product people

Ask the people who’ve done it.

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Answers quote and cite the source notes

01 — TopicsFourteen drawers, sorted.

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Open drawer · 11

Metrics, data & experimentation

316 notes · 58 people · 2005–2026
Lenny’s Newsletter · Free post♥ 224

What is good retention?

Jun 9, 2020 · 12 min

“Hello, and welcome to the free monthly editionof my weekly newsletter. I’m Lenny, and each week I tackle reader questions about product, growth, working with humans, and anything else that’s stressing you out at the office. Q: What do you consider GOOD and GREAT retention? “Great retention is the scalable way to grow a product. It’s the best indicator of product-market fit, it is the most important factor in a user’s lifetime value…”

Lenny’s Newsletter · Free post♥ 1,022

How Duolingo reignited user growth

Feb 28, 2023 · 21 min

Jorge Mazal, former CPO of Duolingo, recounts how the company reversed a slide in daily active user growth and eventually grew DAU about 4.5x over four years. The journey began with failed attempts: a…

@ttorres · Teresa Torres on X♥ 97
"The only way to know if our AI products and workflows are any good is with evals." 💡 If you're using AI to write PRDs, analyze customer feedback, or build customer-facing AI products, you need to understand evals. This guide breaks down what evals actually are and why product teams should be…
Lenny’s Podcast97 min

The ultimate guide to AEO: How to get ChatGPT to recommend your product

Ethan Smith · Sep 14, 2025
Key learnings
  • Everything that works in traditional SEO also works for AEO, so start with landing pages targeting high-volume keywords before…
  • In LLM answers you win by being mentioned across many citations, not by ranking first, so pursue multiple third-party mentions…
  • Early-stage companies can win in AEO quickly, since a single citation from a Reddit thread, YouTube video, or blog can get you…
Lenny’s Podcast96 min

The ultimate guide to A/B testing

Ronny Kohavi · Jul 27, 2023
Key learnings
  • Test every code change, since even small bug fixes or tiny UI tweaks can have surprising, large impact on key metrics.
  • Expect most ideas to fail: roughly two-thirds to over 90% of experiments in his experience did not move the target metric, so…
  • Allocate a portion of experiments to high-risk, high-reward bets, accepting that about 80% will fail, while keeping most work…
Lenny’s Newsletter · Free post♥ 250

What is a good activation rate

Oct 25, 2022 · 14 min

Lenny Rachitsky and growth advisor Yuriy Timen ran a benchmarking survey of over 500 product teams to answer what counts as a good activation rate. The article defines activation as the share of new users who reach a…

@ttorres · Teresa Torres on X♥ 9
💭 "I wish I could click on this card and be like, 'Clean this up.'" When a customer pointed out a flat, unstructured branch in her AI-generated opportunity solution tree, it sparked a three-week journey to fix the problem at its source. Here's what you'll learn from this article: How one customer…

02 — FrameworksModels, annotated.

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03 — PeopleWho wrote the notes.

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04 — QuestionsAnswered from the notes.

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Where notes come from

NewsletterLenny’s Newsletter106 free posts, with a longer excerpt.
Subscriber postsSummary only229 paid posts: our summary, at most two short quotes, and a link.
PodcastLenny’s Podcast322 episodes, each with 5–8 key learnings and timestamps.
EssaysSVPG · The Beautiful Mess499 essays from Marty Cagan and John Cutler.
Substack & blogsShreyas · Julie · Jason · Hiten577 essays and posts from independent writers.
XPosts on product58 posts, filtered for product relevance.