This post is for Day 16 of [Merpay & Mercoin Advent Calendar 2025](https://engineering.mercari.com/blog/entry/20251126-m

Mercari's platform is a resource for developers and technology enthusiasts, offering insights into engineering challenges, technology stack, and culture at Mercari. Through articles, tech talks, and open-source contributions, Mercari offers insights into building innovative and scalable technology solutions. Developers can learn about Mercari's engineering culture, agile methodologies, and contributions to the broader tech community.

Mercari Engineering

Mercari's Growth Platform team implemented Server-Driven UI (SDUI) architecture through a feature called EGP Card to accelerate campaign deployment and reduce time-to-market. The solution allows UI configuration to be controlled remotely via JSON schemas rendered natively on iOS, Android, Web, and Flutter, eliminating the need for app releases when updating campaign designs. Key implementation challenges included versioning and backwards compatibility, cross-platform rendering consistency, personalization through placeholder replacement, and state management for interactive components. The team addressed these through graceful degradation, comprehensive testing automation, AI-assisted code generation, and custom component patterns. While requiring significant upfront investment, the SDUI approach dramatically reduced campaign iteration time from weeks to minutes and enabled rapid A/B testing.

Supercharging User Engagement: How Mercari is Using Server-Driven UI to Reduce Time-to-Market