Beyond Simple Similarity: How Sequential Two-Tower Neural Networks Revolutionize Product Recommendations

Roman Dušek Miroslav Tryzna Jonathan Senin
Roman Dušek Miroslav Tryzna Jonathan Senin
Powering product recommendations with Sequential Two-Tower Neural Networks

In the dynamic world of ecommerce, shopper behavior is rarely static. Customers’ needs and interests evolve over time, and you need to meet those preferences if you hope to keep them coming back to your brand. 

We’ve previously covered the benefits of Two-Tower Neural Networks (2TNN) and how they offer significant improvements over traditional Alternating Least Squares (ALS) for product recommendations. In particular, neural networks can understand user preferences to show more relevant products.

But the story doesn’t end there. In the past few years, we’ve witnessed amazing advances in AI science, which currently powers agentic products like ChatGPT or Gemini. We use the same neural networks and deep learning techniques to power Recommendations+ — our next-generation recommendation engine — enabling Loomi AI to understand each customer’s journey and recommend products just for that individual customer. By leveraging a sequential understanding of each customer, Recommendations+ ultimately drives higher engagement and conversion. 

Read on to understand how this technology will truly revolutionize personalization. 

The Power of Sequence: Moving Beyond Static Recommendations

Imagine a shopper is browsing for a new coffee maker. With ALS, recommendations might be based on their general purchase history and users with similar overall profiles. However, with a sequential model, we understand the entire journey. Did they just view several pour-over coffee makers? Did they recently search for coffee beans? Are they now looking at kettles? A sequential 2TNN, unlike ALS, recognizes these patterns and adjusts recommendations in real time, suggesting complementary items like filters, grinders, or even coffee mugs that align with their current shopping sequence.

Sequential Two-Tower Neural Networks determining the next best product recommendation based on user actions

Here’s how sequential 2TNNs, particularly those leveraging transformer architectures, outperform ALS in capturing this dynamic user behavior:

Contextual Understanding, Not Just Similarity 

Unlike ALS, which recommends items based on overall similarity without considering interaction order, sequential models leverage the sequence of user actions to predict what the user is most likely to click or purchase next. They don’t just react to the latest interaction but understand the broader context, such as the user’s browsing path, transitions between items, and evolving intent. 

This allows the recommendation engines to guide users toward conversions by surfacing recommendations that align with their current journey, rather than just suggesting similar products. This journey-aware approach is critical for effective personalization.

Capturing High-Order Dependencies With Transformers 

The sequential models used in 2TNN can learn high-order dependencies across a sequence of interactions. This means they’re not limited to immediate past actions but can incorporate long-term dependencies and complex behavioral patterns. 

Additionally, transformers feature a self-attention mechanism that weighs interactions differently based on their relevance, which helps capture both local and global dependencies effectively. This flexibility leads to more nuanced recommendations that account for subtle shifts in user behavior.   

Overview of how Sequential Two-Tower Neural Networks work with product recommendations

Data Efficiency and Granular Personalization

2TNN benefit from increased data as they can extract more patterns with a non-linear capacity of neural layers. With larger datasets, they become better at distinguishing subtle differences in user preferences (i.e., more granular). They also learn to recommend items based on the specific context of a user’s recent sequence of interactions, such as browsing history or purchase patterns. 

The non-linear nature of neural networks, especially in the transformer architecture, allows 2TNNs to extract richer insights from user data. The more data, the more refined and personalized the recommendations become, moving beyond broad categories to truly individual preferences.

Visualizing the Difference: Retrieval Processes Compared

Comparison between standard product recommendations and Bloomreach's Recommendations+

The image above visually illustrates the key difference in how ALS and our Sequential Two-Tower Neural Network retrieve recommendations.

Imagine a customer leaving a trail of breadcrumbs as they browse. ALS picks up all those breadcrumbs and tries to find other customers who left similar trails overall. It then suggests products based on what those similar customers interacted with in the past. Think of it as a broad, general approach, like recommending a coffee maker to someone who once bought coffee beans, regardless of whether they’re currently looking at espresso machines or tea kettles. It’s useful for understanding general preferences, but it misses the nuances of a specific shopping journey.

Now imagine that same customer leaving those breadcrumbs, but this time, you’re following their trail step by step. You see them first looking at French presses, then browsing different coffee bean types, and finally, they pause on a page with milk frothers. The 2TNN acts like that attentive observer. It understands the sequence of actions and recognizes the evolving intent.  Instead of just recommending any coffee-related product, it understands the context of the current session and suggests something highly relevant, like a specific type of milk or a cleaning kit for their potential French press. It’s all about understanding the journey and providing personalized recommendations in real time that align with the customer’s immediate needs.

How Bloomreach Drives Impact for Ecommerce Businesses

Bloomreach Engagement is the only autonomous marketing platform that incorporates the latest AI techniques, such as sequential modeling via transformers, to power personalized product recommendations across all channels. What’s more, we make this advanced AI easily accessible for non-technical marketers so they can still deliver campaigns that improve business metrics. 

These AI innovations have culminated in our release of Recommendations+, a next-generation recommendation engine that incrementally improves product click-through rates by 9% or more. Recommendations+ can help marketers: 

  • Drive greater results: With Recommendations+, you’ll deliver more personalized recommendations, resulting in higher click-through rates (CTR) and product engagement. In turn, this increased CTR will lead to improved purchase conversion rates, more time on site, higher lifetime value for loyal customers, better conversions for first-time anonymous visitors, and more. 
  • Reach customers everywhere: Consumers can interact with your products from anywhere, whether it’s email, mobile, or web. With our built-in customer data engine, you can deploy Recommendations+ on all of these channels — including new and emerging ones like RCS — to maximize click-through rate. 
  • Personalize in real time: Recommendations+ improves CTR while still delivering individualized recommendations in real time. With Engagement’s real-time architecture, you’ll learn and adapt after every click to keep your recommendations consistently relevant. 
  • Launch quickly: We’ve built Recommendations+ so that any non-technical marketer can use it, featuring a visual editor to create recommendation widgets that can be placed within any channel. 

Bloomreach Leads the Way in Personalized Ecommerce

At Bloomreach, we’re committed to pushing the boundaries of personalization. Our ongoing research into Two-Tower Neural Networks and sequential recommendation techniques is at the forefront of this innovation. As we continue to explore and refine these powerful models, we’re excited to bring more sophisticated and effective product recommendation capabilities to the Bloomreach Engagement platform like Recommendations+.

Building upon the advancements in sequential understanding, we’re also actively developing a personalized ranking layer that will further refine our recommendation engine. This new layer will incorporate richer user context, such as demographics, past purchase history, and real-time behavioral signals, alongside a deeper understanding of item content like metadata, attributes, and even visual features. By combining these elements, we aim to create an even more nuanced and personalized recommendation experience, ensuring that users are presented with the most relevant and desirable items at every stage of their shopping journey. This continuous evolution of our models will allow us to deliver unparalleled personalization and drive even greater value for our customers.

Stay tuned for further updates on our research, A/B testing results, and the exciting advancements we are making in the realm of AI-powered personalization for ecommerce. And be sure to check out Recommendations+ to start delivering individually personalized recommendations to your customers today.

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Roman Dušek

Machine Learning Engineer, Engagement at Bloomreach

Roman is a Machine Learning Scientist with 4 years of experience in search and recommendations, and previously worked at the leading ecommerce marketplaces in the Czech Republic and Poland.

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Miroslav Tryzna

Product Manager at Bloomreach

As a mathematician turned data analytics expert and product manager of AI features, Miro has always had a passion for leveraging numbers to drive meaningful insights. Miro’s time is dedicated to harnessing the power of data to develop innovative AI-driven solutions and lead product management efforts for cutting edge technologies. Miro is known for a meticulous attention to detail, strategic mindset, and exceptional ability to translate complex technical concepts into user friendly features. 

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Jonathan Senin

Senior Product Marketing Manager, Bloomreach Engagement

Jonathan Senin is a Senior Product Marketing Manager at Bloomreach. He has over seven years of experience in ecommerce martech across personalization platforms, CDPs, chatbots, and more. Jonathan was super excited to join Bloomreach because of its product strength: a truly omni-channel platform that can do it all. Outside of work, Jonathan likes to play tennis, cuddle with his dog Luna, and play Gran Turismo 7.

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