Duopoly Dynamics in Online Grocery

Duopoly is what online grocery marketplaces look like after the land grab, because the model rewards the two apps that get dense enough to make delivery faster, cheaper, and more reliable than everyone else. Once a platform has lots of merchants, lots of shoppers, and enough couriers to batch nearby orders, it improves ETAs and cost per drop, which pulls in even more demand and makes smaller rivals increasingly hard to fund or operate.

• In grocery marketplaces, scale is not abstract. It means more stores signed by local sales teams, more orders flowing through the app, and more chances to combine deliveries on one route. That is why drops per trip is a core profit lever, and why dense networks tend to pull ahead market by market.
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• The pattern shows up in practice. In U.S. online grocery, Walmart and Instacart held the top two positions in 2022 at 38% and 29% share, while Uber Eats and DoorDash were much smaller at about 5% each. That kind of share gap makes it hard for a long tail of marketplaces to sustain comparable service levels.
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• Even winners often push beyond pure marketplace. Instacart layered on retailer software and ads, while Rappi invested in dark kitchens and multi vertical delivery. That expansion reflects the limit of a pure middleman model, marketplaces are great at aggregating demand, but weaker at improving gross margin without deeper control of supply.
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The likely next step is fewer pure grocery marketplaces and more hybrid leaders that use duopoly scale as a base, then add software, advertising, private supply, or owned fulfillment. The durable winners will be the ones that turn route density into a broader economic moat, not just more orders in the same app.