⚡ What fits where:

PostgreSQL

• Great for core transactional data:

  • Users, drivers, payments, invoices, compliance.

  • Ensures ACID compliance (you don’t want payments lost or inconsistent).

• Rich querying + joins + analytics (Postgres + extensions like PostGIS for geospatial queries).

  • Example: “Find all drivers within 2km of this point.”

MongoDB

• Great for event logging at scale:

  • GPS pings (every 2–5 seconds per ride).

  • Session logs, app telemetry, semi-structured JSON-like ride documents.

• Handles massive write throughput and horizontal scaling better.