An e-commerce platform built around automated pricing, marketplace data and the bol.com Buy Box.
The project
Growdt was developed to give marketplace sellers more control over pricing and profitability on bol.com.
At the centre of the platform is the Growdt Engine: a repricing system that continuously evaluates marketplace conditions and automatically adjusts product prices within the seller’s rules.
| 91 has been responsible for the software development and architecture behind the platform.
That includes the pricing engine, the integration with bol.com, processing marketplace and competitor data, the seller application and the infrastructure required to make pricing decisions continuously across large product catalogues.
The Growdt Engine
Most repricing starts with a relatively simple principle: monitor competing prices and adjust your own price in response.
Growdt was built differently.
The engine uses the actual Buy Box outcome as feedback for its pricing decisions. Winning the Buy Box is therefore not necessarily the end of a repricing cycle.
Once an offer is winning, Growdt can test whether a higher selling price is possible while retaining the Buy Box.
If an increase causes the Buy Box to be lost, the engine can use previous results to move back towards a known winning price.
The result is a continuous process of finding the available pricing range rather than simply following the lowest competitor.
Connected directly to bol.com
Growdt is built on the official bol.com API.
The platform continuously processes information about products, prices, competitors and Buy Box outcomes and combines this with the pricing rules configured by the seller.
Every pricing decision has to remain within those rules, including minimum and maximum prices and the selected pricing strategy.
The engine also has to operate within the technical limits and behaviour of the marketplace itself. API capacity, processing cycles and the time required for marketplace changes to become visible all influence how the system operates.
Growdt was engineered around those conditions rather than assuming marketplace data is always immediate.
Finding the highest winning price
One of the important findings during development was confirming that the lowest price does not always win the Buy Box.
In live testing, Growdt repeatedly retained the Buy Box while selling above competing offers.
Rather than treating the competitor’s price as the maximum possible selling price, the engine can therefore test whether additional pricing room exists.
In one live test, Growdt retained the Buy Box at €5.91 while a competing seller was priced at €5.78.
The objective is not simply to change prices quickly. It is to use marketplace feedback to find a better balance between Buy Box position and selling price.
Continuous marketplace processing
Marketplace pricing changes constantly.
Competitors adjust their prices, multiple repricers can operate against each other and Buy Box outcomes can change independently of price.
Growdt therefore maintains the context of previous pricing decisions and their outcomes rather than treating every marketplace change as an isolated event.
This allows the engine to react to competitive pressure, test higher prices when conditions allow it and use previous results when a price movement does not produce the intended outcome.
Across large catalogues, this means processing thousands of products and large numbers of marketplace checks, pricing decisions and updates continuously.
The underlying architecture was designed around that continuous processing.
More than repricing
The Growdt Engine sits within a wider platform for managing marketplace operations.
Sellers can manage products, pricing strategies and price boundaries, while dashboards provide visibility into Buy Box performance, pricing activity and additional margin.
Pricing decisions are recorded so sellers can understand how individual offers have been repriced and how the engine is operating across their assortment.
The same architecture also provides the foundation for additional marketplace functionality and automation beyond repricing.
Building an e-commerce platform?
| 91 designs and develops e-commerce software, marketplace integrations and operational platforms.
From individual marketplace integrations to complete platforms and automation engines, we build systems where products, data and business rules need to work together at scale.
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