How Chinese Developers Built a Rapid COVID-19 Travel Query Tool in One Day

At the start of 2020, amid the COVID-19 outbreak, a group of developers decided to use their coding skills to help the public quickly verify whether they had traveled with a confirmed patient.

The resulting "COVID-19 Travel Companion Query Tool" allows users to input a date, train or flight number, and region to check for possible exposure. The tool aggregates publicly released passenger information, stores it in a database, and provides a simple search interface.

In an interview, CTO Tong Yong'ao explained that the initial motivation was personal: the existing information was presented as images, making manual lookup error‑prone and time‑consuming. By extracting the data and building a searchable tool, the process became far more efficient.

The development team was formed quickly from long‑time online friends and a few volunteers. After a brief sketch of the UI was shared in a chat group, tasks for front‑end, back‑end, and data collection were assigned immediately.

Technically, the solution is straightforward. Existing images and text were normalized into a unified database, and a simple retrieval service was built on top of it. The core fields include transportation mode (train, plane, bus, taxi), date, and route.

Development time was astonishingly short: the idea emerged around 11 am on January 27, a functional front‑end and back‑end were ready by 5 pm, and after six more hours of data entry the tool was shared on social media at 11 pm.

After launch, traffic surged dramatically—450 000 visits on the second day, jumping to millions within hours. The original 1 Mbps, 1 GB server could not handle the load, so the team switched to a third‑party CDN and later generated static pages and data files hosted on Alibaba Cloud OSS to offload the traffic.

Data volume grew to 500‑600 records, with a rigorous verification funnel: initial clues → volunteer collation → internal verification → entry → final review. Both web crawling and manual submissions contribute roughly equally to the dataset.

Challenges included scaling the infrastructure and maintaining data accuracy as the volume increased. The team now focuses on improving data reliability rather than adding new features.

Tong advises developers to treat coding as a tool for solving real‑world problems, not merely a job, and encourages others to create small utilities that address everyday needs.

The article concludes with a call for more developers to contribute similar tools to help combat the pandemic.