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Lenny's Knowledge Sketch · Growth Models & Marketplaces

Building Growth Models & Scaling Marketplaces

Dan Hockenmaier
Head of Strategy & Analytics, Faire · Marketplace Expert
STRATEGY
The Framework

A Growth Model is Your Business Formula

ACQUISITIONRETENTIONMONETIZATION=YOUR REVENUE ENGINE
"50% of the value from building a growth model is simply building the model. It forces you to understand how your business works. You get a spreadsheet that's very hard to fake."
  • Lives in Excel: a formula that represents your entire business
  • Not a forecasting tool, but an opportunity assessment tool
  • Forces brutal clarity: you must understand every assumption
  • Reveals the levers that actually matter for your growth
The Components

What Goes Into a Growth Model

SaaS Basics (3 pillars)
  • Acquisition channels (traffic, conversion, spend)
  • Retention curve (activation rate, monthly survival)
  • Monetization (subscription fee or ARPU)
Transactional Layer
  • Transactions per month (frequency)
  • Average order value (AOV)
  • Unit economics (COGS, CAC, margin)
The pitfallStacking assumptions is dangerous. Marketplaces especially risk "junk in, junk out" when you're trying to model both supply and demand simultaneously. Start with a simple high-level model, then build mini-models per team.
Marketplace Metrics

The 4 North Stars Every Marketplace Needs

  • GMV & Transactions: The ultimate metric that brings supply and demand together
  • Unit Economics: Most early marketplaces have negative or poor unit economics (Instacart, Uber). Understand the path to profitability.
  • Liquidity: Can buyers find what they want? Can sellers find buyers? For Uber: wait time. For commerce: search fill rate. This is THE metric until you have it.
  • Share of Wallet: What % of a customer's total spend comes through you? This drives LTV, retention, and defensibility.
Why share of wallet matters most

Two ways to grow 10% GMV: get 10% more customers OR get 10% more of existing customers' wallet. Take the second. It signals depth, retention, and a defensible moat.

The liquidity threshold

For Uber, there's a magic moment around 4-5 min wait time where the service clicks. Before that threshold, nothing else matters. Focus ruthlessly on liquidity first.

Supply vs. Demand

The Counter-Intuitive Truth

  • Most PMs over-rotate on supply, under-focus on demand
  • Supply feels important early (it is the product initially), but demand is the currency
  • If you own demand, suppliers will always say yes to your marketplace
  • Only acquire supply if you understand its impact on customer experience
"Demand is the only thing that matters. If you can aggregate the demand, you will win. Because suppliers will always say yes if you bring them customers at a profitable rate."
The hidden principleEvery supply acquisition decision must answer: does this meaningfully improve the customer experience? If not, it's waste.
Contrarian

Marketplace Myths Debunked

✗You should focus on supply-side product firstINSTEAD →✓ Obsess over the demand-side experience. Supply will follow if demand is strong enough.
✗Expand to many categories / geographies quicklyINSTEAD →✓ Narrow scope ruthlessly. Build liquidity in one category or geography first, then scale.
✗Unit economics must be positive from day oneINSTEAD →✓ Early marketplaces almost always have negative unit economics. The moat comes later as supply and demand densify.
✗Run a marketplace like a SaaS businessINSTEAD →✓ You're a gardener, not a construction worker. Light touch, long feedback loops, ecosystem thinking required.
Based on Dan Hockenmaier's episode on Lenny's Podcast. All ideas on this page are from the episode.Watch on YouTubeFollow @danhockenmaier on X
GO DEEPER IN THE EPISODE
04:01 What is a growth model?07:20 The building blocks of a growth model for your own business10:22 The value in building your own model11:12 The importance of retention over growth14:49 Getting started building your model19:18 The growth model at Thumbtack20:36 The importance of the early user experience for retention25:02 Why is a marketplace a good business?28:23 Health metrics for marketplaces33:47 Supply and demand, and why you shouldn’t neglect demand36:23 The role of ROI equations and how to use them39:16 Why you should tread lightly when working with marketplaces42:43 Expanding marketplaces46:50 How marketplaces can add a SaaS offering, and why adding a marketplace to a SaaS business is trickier49:47 When is there an opportunity to unbundle?54:43 B2B marketplaces56:36 What is fragmentation?58:46 The future of marketplaces
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