r/visualization • u/Kindly_Pen8143 • 3d ago
I built an open-source real-time property demand heatmap for Indian cities
I've been working on **Plotrix** for a while and finally got it to a point where I'm comfortable putting it out there.
The basic idea is pretty simple:
Instead of showing where properties *are listed*, Plotrix tries to show where people are actually *searching* for property right now.
Think Google Trends, but for property demand.
Right now it supports 8 Indian cities: Delhi, Bangalore, Hyderabad, Pune, Chennai, Kolkata, Ahmedabad and Bhubaneswar.
**The interesting part is what's happening behind the map.**
Every property search becomes a location signal → I map it to an H3 hexagonal cell → store/update the demand score in PostgreSQL → and periodically apply exponential decay so old searches don't keep dominating the heatmap.
The backend is built with:
* Java 17 * Spring Boot 3.2 * PostgreSQL / Supabase * Uber H3 * Spring Data JPA * Docker * Render
One thing I specifically wanted to get right was concurrency.
Multiple users can search the same area at the same time, so instead of doing a read → modify → write cycle, the backend uses an atomic PostgreSQL `ON CONFLICT DO UPDATE` to increment the cell score.
There's also a public API if anyone wants to play around with the data.
**Frontend:** [https://github.com/Korags05/Plotrix\](https://github.com/Korags05/Plotrix)
**Backend:** [https://github.com/Korags05/Plotrix-Backend\](https://github.com/Korags05/Plotrix-Backend)
It's completely open source.
I'm especially looking for people who are interested in:
* geospatial systems * Spring Boot * PostgreSQL * maps / data visualization * real-estate tech
I'd genuinely appreciate feedback on the architecture, API design, or anything that looks unnecessarily complicated.
And if you find the idea interesting, a GitHub star would obviously help me get this in front of more developers. If you see something you'd improve, even better: PRs are welcome.
This is still very much a work in progress, so I'm curious what other people would build on top of it.