Carpool

Fills empty seats on commutes people in one Greek prefecture already drive: drivers publish their routes, passengers post where they need to be, and a driver whose route passes nearby gets asked. There is no dispatching and no in-app payment; the driver always accepts explicitly. Go backend and Expo app, in active development.

The problem Link to heading

Outside the big cities there is nothing to match a passenger with the neighbour who drives that road every morning, and the platforms that exist are built around a commission that makes a 40 km commute not worth listing.

What I built Link to heading

Built the whole stack to run on one small machine: Go, PostGIS and a local OSRM extract in Docker, about 330 MiB for the lot, so the running cost of a regional community is a mini PC rather than a routing API bill. Money is a suggestion the app computes and caps, never something it moves.

Implementation Link to heading

  • Two-Stage Geospatial Matching: A direction- and order-aware PostGIS filter narrows candidate routes, then OSRM computes the incremental detour against the driver’s actual itinerary; matched drivers are asked sequentially by push, with timeouts, rather than auctioned.
  • Cost the Car Actually Has: Consumption is derived from the vehicle’s registration document (fuel, engine size, CO₂) instead of typed, and the suggested share is capped so a full car cannot turn a commute into a profit.
  • Recurring Routes as Templates: A weekday commute is published once and materialises into occurrences; each departure carries the car it actually goes out in, so editing a route cannot silently change the plate a passenger is standing at the kerb looking for.
  • Safety Decisions in the Schema: Age gate, moderated bios, closed preference vocabulary, per-trip chat, mutual ratings, plate revealed only after a seat is accepted, and retention periods enforced by scheduled jobs rather than by policy text.
  • Verified End to End: vet, staticcheck and race-clean concurrency packages, 293 app tests, and a fourteen-step scenario that runs from a fresh database against real PostGIS and real OSRM: publish, request, ask, accept, chat, confirm, rate.