Backend platform for a vehicle-fleet management product

Problem

The original prototype mixed business logic, database access and third-party integrations in a single module. New features took weeks and broke old ones; the team had no confidence in deployments.

Approach & architecture

• Introduced a layered architecture — API, application services, domain, infrastructure — with explicit interfaces, so integrations (GPS providers, payments) became swappable adapters.
• Added authentication with scoped API keys and JWT for the web app, per-tenant data isolation and rate limiting.
• Set up CI with linting, type checks and an integration test suite against a real PostgreSQL database, plus zero-downtime deployments.

Result

• Feature lead time went from weeks to days; regression incidents dropped to near zero.
• Public API documented with OpenAPI and used by two partner integrations.
• Sustained 99.9% uptime over the following year.

What made it robust

• Type-checked (mypy strict), 85%+ test coverage on domain and API layers.
• Structured logging, request tracing and alerting on error budgets.
• Documented architecture decisions (ADRs) and an on-call runbook.