This document summarizes four Japanese AdTech companies that use AWS: Dynalyst, fluct, IM-DMP, and UNICORN. Dynalyst uses AWS for real-time bidding and cross-region data processing. fluct is an SSP that processes 30 billion impressions per month on a serverless architecture. IM-DMP utilizes Amazon ECS and Spot Fleet to power its public DMP. UNICORN is a full automated marketing platform that uses AWS for real-time bidding, data analysis, and machine learning.