hkbus.app is a web application utilizes the public transport ETA data from data.gov.hk. The proposal will covers the software stack for achieving extremely low cost to support several thousands and even more users. Then, I will present the outcome and status of marketing, mainly via SEO and social media. In the third part, I will jump into the discussion on contribution by other users and the community status in Telegram, currently with ~1300 users and 7 admins.