Architected and scaled the Toss 'Benefit Tab' frontend, leading 200+ data-driven product iterations through continuous A/B testing on a complex hybrid stack of Web (Next.js) and React Native to drive a 42% MAU increase (4.9M to 7M) and secure key revenue streams pivotal to the company's EBITDA turnaround.
Rewarded Ads
Built and maintained a suite of incentivized ad units — CPI Offerwall, opt-in engagement formats (Step Counter, Lucky Draw, Lucky Quiz, Money Alarm) — optimizing for cost-per-engagement (CPE) and user retention within the Benefit Tab inventory.
Launched high-yield rewarded placements including Live Commerce (shoppable video ads) and Weekly Visit Mission (recurring engagement loops), scaling DAU from 0 to 2.2M and driving approximately KRW 4B in monthly recurring ad revenue.
Display Ads
Engineered ad serving infrastructure for display ad inventory across standard banner, full-screen interstitial, and in-stream video ad formats on a hybrid React/React Native ad surface — handling 300K UV/min peak traffic without horizontal scaling of SSR instances.
Reduced First Contentful Paint (FCP) on the primary monetization placement by over 50% to under 800ms, directly improving ad viewability rates and CTR in high-impression scenarios.
Architected a scalable video ad delivery pipeline using HLS adaptive bitrate streaming and chunk-based segmentation, reducing ad request waterfall calls by 90% and supporting 50x peak traffic over the legacy MP4 VAST-based system.
Achieved sub-16ms frame rendering for rich media creatives in React Native by offloading animation workloads from the JS bridge to the native UI thread via SharedValue and Worklets, ensuring smooth ad playback at 60fps.
B2B Platform (Toss Ads)
Redesigned authentication logic to enable scalable account structures under the Business Group model, improved clarity and usability of campaign performance dashboards, and supported seamless integration across Toss's B2B platforms — Ads, Pay, and Commerce.
Led major UX overhauls across both advertiser-facing and admin-side workflows, applying consistent design systems and real-time validation to reduce user errors and streamline campaign creation.
Growth & Acquisition
Rebuilt the Toss Ads marketing site, integrating lead capture, analytics, and sales pipeline — resulting in a 2x increase in advertiser leads and a more efficient acquisition funnel.