Building Spatial Memory

I spent three months building a Pinterest for the physical world.

The idea is simple. You leave digital notes, photos, or stories at specific GPS coordinates. People can only see them when they physically stand in that exact spot. It turns the real world into a collection of digital time capsules.

Building a location-based app is harder than it looks. Here is what I learned about the tech stack.

The Spatial Database You cannot just store latitude and longitude as simple numbers if you want to scale. You need spatial indexes. I used PostGIS with PostgreSQL.

It handles:

  • Spatial indexing with R-tree
  • Built-in distance calculations
  • Fast proximity queries

If you need to find memories within 50 meters of a user, PostGIS does the heavy lifting.

The Caching Strategy Popular tourist spots get too many requests. Hitting the database every two seconds is bad for performance. I used Redis GEO commands to cache memory IDs in busy areas.

A pro tip: Do not cache the entire object in Redis. Only cache the IDs. This keeps your memory usage low and cuts query time from 20ms to 2ms.

The Upload Pattern If your server handles every photo upload, it will crash under load. I used a two-phase upload pattern:

  • The client asks the server for a pre-signed URL
  • The client uploads the file directly to Cloudflare R2
  • The client tells the server when the upload is finished

I chose R2 over S3 because there are no egress fees. This saves money when users download media.

What Worked

  • PostGIS and Redis GEO make spatial queries fast.
  • Direct-to-R2 uploads allow the backend to scale.
  • Go and Gin provide high performance with low memory use.
  • Progressive privacy (Private, Friends, or Public) protects users.

What Went Wrong

  • GPS accuracy is inconsistent in cities with tall buildings.
  • The "cold start" problem is real. The app needs many users to feel alive.
  • Content moderation requires constant attention.

Building this taught me that physical location is an underrated dimension for social apps. Digital content feels more meaningful when it is tied to a real place.

Source: https://dev.to/kevinten10/building-spatial-memory-why-i-built-a-pinterest-for-the-physical-world-and-what-i-learned-bpm

Optional learning community: https://t.me/GyaanSetuAi