Mercari leverages Google's vector search technology to create a new marketplace

Mercari is likely one of the most profitable market providers lately, with 5.three million energetic customers within the US and 20 million energetic customers in Japan. In Oct 2021, the corporate launched a brand new service Mercari Outlets in Japan that permits small enterprise house owners and people to open their e-commerce portal in three minutes. On the core of the brand new service, Mercari launched Google’s vector search expertise to comprehend the essential half: creating a brand new market for small outlets utilizing “similarity”.

The Problem: assortment of retailers does not make a market

On the time of the launch, Mercari Outlets was only a assortment of small e-commerce websites the place buyers may solely see the objects bought by every store one after the other. For the consumers, it was a considerably painful expertise to return to the highest web page and select a store every time. This loses a very powerful worth of the service; an pleasant procuring expertise for the consumers.

Consumers would love one thing like “an actual market on smartphones” the place they will simply browse tons of of things from all kinds of retailers with a single finger gesture. However how do you handle the relationships throughout all of the objects to comprehend the expertise? You would want to rigorously outline thousands and thousands of merchandise classes and SKUs shared throughout the 1000’s of sellers, and preserve sustaining all of it by handbook operation of assist workers. It additionally requires the sellers to go looking and select the precise class for every merchandise to promote. That is the way in which conventional market providers are constructed, involving a lot operational value, and likewise dropping one other key worth of Mercari Outlets that anybody can construct an e-commerce web site inside three minutes.

How about utilizing a advice system? The favored advice algorithm equivalent to collaborative filtering normally requires giant buy or click on histories to suggest different objects, and does not work properly for recommending new objects or long-tail objects that do not have any relationship with current objects. Additionally, collaborative filtering solely memorizes the relationships between the objects, equivalent to “many shoppers buy/view these different objects additionally”. Which means, it does not really make any suggestions with insights by wanting on the merchandise descriptions, names, photos or many different facet options.

So Mercari determined to introduce a brand new manner: utilizing “similarity” to create a market. 

A brand new market created by similarity

What does it imply by similarity? For instance, you possibly can outline a vector (an inventory of numbers) with three parts (zero.1, zero.02, zero.03) to symbolize an merchandise that has 10% affinity to the idea of “contemporary”, 2% to “vegetable”, and 30% to “tomato”. This vector represents the that means or semantics of “a contemporary tomato” as an merchandise. When you search close to vectors round it, these objects would even have related that means or semantics – you’ll discover different contemporary tomatoes (notice: it is a simplified clarification of the idea and the precise vectors have a lot advanced vector area). 

This similarity between vectors exemplifies in Mericari Outlets that permits the patron to browse all the same objects collected on a web page. You needn’t outline and replace merchandise classes and SKUs manually to attach between the thousands and thousands of things from 1000’s of sellers. As an alternative, machine studying (ML) algorithms extract the vectors from every merchandise robotically, each time a vendor provides a brand new merchandise or updates an merchandise. That is precisely the identical manner Google makes use of for locating related contents on Search, YouTube, Play and different providers; known as Vector Search.

Enabled by the expertise, now the consumers of Mercari Outlets can simply browse related objects bought by totally different outlets on the identical web page.

Vector search made simple with Matching Engine

Let’s check out how Mercari constructed utilizing the vector search expertise. With analytics outcomes and experiments, they discovered that the merchandise description written by the sellers represents the worth of every merchandise properly, in comparison with different options such because the merchandise photos. So that they determined to make use of merchandise description texts to extract the characteristic vector of every merchandise. Thus, of Mercari Outlets is organized by “how objects are related to one another within the textual content description”.

For extracting the textual content characteristic vector, they used a word2vec mannequin mixed with TF-IDF. Mercari additionally tried different fashions equivalent to BERT, however they determined to make use of word2vec because it’s easy and lightweighted, appropriate for manufacturing use with much less GPU value for prediction.

There was one other problem. Constructing a manufacturing vector search infrastructure shouldn’t be a straightforward process. Up to now, Mercari constructed their very own vector search from scratch for a picture search service. It took for them to assign a devoted DevOps engineer, allow them to construct Kubernetes servers, design and preserve the service. Additionally, they needed to construct and function a knowledge pipeline for steady index replace. To maintain the search outcomes contemporary, you should replace the vector search index each hour with newly added objects utilizing the info pipeline. This pipeline had some incidents up to now and consumed DevOps engineers’ sources. Contemplating these elements, it was virtually not possible for Mercari Outlets so as to add a brand new vector search underneath a restricted useful resource. 

As an alternative of constructing it from scratch, they launched Vertex AI Matching Engine. It is a totally managed service that shares the identical vector search backend with the main Google providers equivalent to Google Search, YouTube and Play. So there isn’t a have to implement the infrastructure from scratch, preserve it, and design and run the index replace pipeline by your self. But, you possibly can rapidly reap the benefits of the responsiveness, accuracy, scalability and availability of Google’s newest vector search expertise.

The characteristic extraction pipeline

Mercari Outlets’ search service has two elements: 1) characteristic extraction pipeline and a pair of) vector search service. Let’s examine how every element works.

The characteristic extraction pipeline is outlined with Vertex AI Pipelines, and is invoked by Cloud Scheduler and Cloud Capabilities periodically to provoke the next course of:

1. Get merchandise information: The pipeline makes a question BigQuery to fetch the up to date merchandise information

2. Extract characteristic vector: The pipeline runs predictions on the info with the word2vec mannequin to extract characteristic vectors

3. Replace index: The pipeline calls Matching Engine APIs for including the characteristic vectors to the vector index. The vectors are additionally saved to Cloud Bigtable

The next is the precise definition of the characteristic extraction pipeline on Vertex AI Pipelines:

Vector search service

The second element is the vector search service that works within the following method:

1. Consumer makes a question: a consumer makes a question to the Cloud Run frontend specifying an merchandise id

2. Get the characteristic vector: get a characteristic vector of the merchandise from Bigtable

3. Discover related objects: utilizing Matching Engine API, discover related objects with the characteristic vector

4. Returns the same objects: returns merchandise ids of the same objects

By introducing Matching Engine, Mercari Outlets was capable of construct the manufacturing vector search service inside a few months. As of 1 month after launching the service, they have not seen any incidents. From improvement to manufacturing, solely a single ML engineer (the writer) implements and operates the entire service.

Trying forward

With the profitable introduction, Mercari Outlets is now engaged on including extra functionalities and increasing the service to future store tasks. For instance, Matching Engine has a filter vector match operate that applies easy filters to the search outcomes.  With this operate, they might solely present “on sale” objects, or exclude objects from particular outlets. Additionally, Matching Engine will assist a streaming index replace quickly that might permit the customers to search out objects as quickly as they’re added by the sellers. Vertex AI Characteristic Retailer seems enticing too as a substitute for the Cloud Bigtable because the repository of characteristic vectors with its extra performance together with characteristic monitoring for higher observability on the service high quality. 

With these Google Cloud applied sciences and merchandise, Mercari can flip their new concepts into actuality with much less time and sources, including important worth to their enterprise.