우아한형제들 / ai

Delivering the Future: 글로벌 해커톤 2025, 준비부터 운영까지 | 우아한형제들 기술블로그 (opens in new tab)

The Global Hackathon 2025 served as a massive collaborative initiative to unite over 270 technical employees from seven global entities under DeliveryHero’s umbrella, including Woowa Brothers. By leveraging the community-building expertise of the Woowahan DevRel team, the event successfully bridged geographical and technical gaps to foster innovation in "Delivering the Future." The hackathon concluded with high-level recognition from global leadership and a strategic partnership with Google Cloud, demonstrating the power of synchronized global technical synergy. ## Strategic Planning and Global Coordination * The event adopted a hybrid "Base Camp" model, where participants worked from their local entity offices while staying connected through 24-hour live streaming and centralized online channels. * Organizers meticulously navigated the logistical hurdles of spanning 70 countries, including coordinating across vastly different time zones and respecting local public holidays and vacation seasons. * Efficiency was maintained through a decentralized communication strategy, using entity-specific meetings and comprehensive guidebooks rather than frequent global meetings to prevent "meeting fatigue" across time zones. ## Technical Infrastructure and Regulatory Compliance * To accommodate diverse technical preferences, the infrastructure had to support various stacks, including AWS, Google Cloud Platform (GCP), and specific machine learning models. * The central organization team addressed complex regulatory challenges, ensuring all sandbox environments complied with strict global security standards and GDPR (EU General Data Protection Regulation). * A strategic partnership with Google Cloud provided a standardized Google AI-based environment, enabling teams to experiment rapidly with mature tools and cloud-native services. ## Local Operations and Cross-Entity Collaboration * Physical office spaces were transformed into immersive hackathon hubs to maintain the high-intensity atmosphere characteristic of offline coding marathons. * The event encouraged "office sharing" between entities located in the same city and even supported travel for members to join different regional base camps, fostering a truly global networking culture. * Local supporters used standardized checklists and operational frameworks to ensure a consistent experience for participants, whether they were in Seoul, Berlin, or Dubai. Building a successful global technical event requires a delicate balance between centralized infrastructure and local autonomy. For organizations operating across multiple regions, investing in shared technical sandboxes and robust communication frameworks is essential for turning fragmented local talent into a unified global innovation engine.

“함께 구매하면 좋은 상품” 추천 모델 고도화 | 우아한형제들 기술블로그 (opens in new tab)

Baedal Minjok (Baemin) has significantly improved its cart recommendation system by transitioning from a basic Item2Vec model to a sophisticated two-stage architecture that combines graph-based embeddings with Transformer sequence modeling. This evolution addresses the "substitutability bias" and lack of sequential context found in previous methods, allowing the system to understand the specific intent behind a user's shopping journey. By moving beyond simple item similarity, the new model effectively identifies cross-selling opportunities that align with the logical flow of a customer's purchase behavior. ### Limitations of the Item2Vec Approach * **Substitutability Bias:** The original Item2Vec model, based on the Skip-gram architecture, tended to map items from the same category into similar vector spaces. This resulted in recommending alternative brands of the same product (e.g., suggesting another brand of milk) rather than complementary goods (e.g., cereal or bread). * **Loss of Sequential Context:** Because Item2Vec treats a basket of goods as a "bag of words," it ignores the order in which items are added. This prevents the model from distinguishing between different user intents, such as a user starting with meat to grill versus a user starting with ingredients for a stew. * **Failure in Cross-Selling:** The primary goal of cart recommendations is to encourage cross-selling, but the reliance on embedding similarity alone limited the diversity of suggestions, often trapping users within a single product category. ### Stage 1: Graph-Based Product and Category Embeddings * **Node2Vec Implementation:** To combat data sparsity and the "long-tail" problem where many items have low purchase frequency, the team utilized Node2Vec. This method uses random walks to generate sequences that help the model learn structural relationships even when direct transaction data is thin. * **Heterogeneous Graph Construction:** The graph consists of both "Item Nodes" and "Category Nodes." Connecting items to their respective categories allows the system to generate initial vectors for new or low-volume products that lack sufficient historical purchase data. * **Association Rule Weighting:** Rather than using simple co-occurrence counts for edge weights, the team applied Association Rules. This ensures that weights reflect the actual strength of the complementary relationship, preventing popular "mega-hit" items from dominating all recommendation results. ### Stage 2: Transformer-Based Sequence Recommendation * **Capturing Purchase Context:** The second stage employs a Transformer model to analyze the sequence of items currently in the user's cart. This architecture is specifically designed to understand how the meaning of an item changes based on what preceded it. * **Next Item Prediction:** Using the pre-trained embeddings from Stage 1 as inputs, the Transformer predicts the most likely "next item" a user will add. This allows the system to provide dynamic recommendations that evolve as the user continues to shop. * **Integration of Category Data:** By feeding both item-level and category-level embeddings into the Transformer, the model maintains a high level of accuracy even when a user interacts with niche products, as the category context provides a fallback for the recommendation logic. ### Practical Conclusion For production-scale recommendation systems, relying solely on item similarity often leads to redundant suggestions that do not drive incremental sales. By decoupling the learning of structural relationships (via graphs) from the learning of temporal intent (via Transformers), engineers can build a system that is robust against data sparsity while remaining highly sensitive to the immediate context of a user's session. This two-stage approach is recommended for e-commerce environments where cross-category discovery is a key business metric.

AI와 함께하는 테스트 자동화: 플러그인 개발기 | 우아한형제들 기술블로그 (opens in new tab)

This blog post explores how a development team at Woowahan Tech successfully automated the creation of 100 unit tests in just 30 minutes by combining a custom IntelliJ plugin with Amazon Q. The author argues that while full AI automation often fails in complex multi-module environments, a hybrid approach using "compile-guaranteed templates" ensures high success rates and maintains operational stability. This strategy allows developers to bypass repetitive setup tasks while leveraging AI for logic implementation within a strictly defined, valid structure. ### Evaluating AI Assistants for Testing * The team compared various AI tools including GitHub Copilot, Cursor, and Amazon Q to determine which best fit their existing IntelliJ-based workflow. * Amazon Q was selected for its superior understanding of the entire project context and its ability to integrate seamlessly as a plugin without requiring a switch to a new IDE. * Initial manual use of AI assistants highlighted repetitive patterns: developers had to constantly specify team conventions (Kotest FunSpec, MockK) and manually fix build errors in 15% of the generated code. * On average, it took 10 minutes per class to generate and refine tests manually, prompting the team to seek a more automated solution via a custom plugin. ### The Pitfalls of Full Automation * The first version of the custom plugin attempted to generate complete test files by gathering class metadata through PSI (Program Structure Interface) and sending it to the Gemini API. * Pilot tests revealed a 90% compilation failure rate, as the AI frequently generated incorrect imports, hallucinated non-existent fields, or used mismatched data types. * A critical issue was the "loss of existing tests," where the AI-generated output would completely overwrite previous work rather than appending to it. * In complex multi-module projects, the AI struggled to identify the correct classes when multiple modules contained identical class names, leading to significant manual correction time. ### Shifting to Compile-Guaranteed Templates * To overcome the limitations of full automation, the team pivoted to a "template first" approach where the plugin generates a valid, compilable shell for the test. * The plugin handles the complex infrastructure of the test file, including correct imports, MockK setups, and empty test stubs for every method in the target class. * This approach reduces the AI's "hallucination surface" by providing it with a predefined structure, allowing tools like Amazon Q to focus solely on filling in the implementation details. * By automating the 1-minute setup and letting the AI handle the 2-minute implementation phase, the team achieved a 97% success rate across 100 test cases. ### Practical Conclusion For teams looking to improve test coverage in large-scale repositories, the most effective strategy is to use IDE plugins to automate context gathering and boilerplate generation. By providing the AI with a structurally sound template, developers can eliminate compilation errors and significantly reduce the time spent on manual refinement, ensuring that even complex edge cases are covered with minimal effort.