Salus

Problem

Backend exercises often stop at the happy-path CRUD: no consistent domain rules, no well-isolated persistence, no real authentication, and not enough tests to prevent regressions.

Salus tackles a small but realistic problem: patient management with domain rules plus user authentication. The repository is public, so every decision described here can be inspected in the code.

Engineering decisions

• Layered architecture, with dependencies pointing toward the domain.
• Domain free of Express and Prisma; use cases never touch Prisma.
• Contracts expressed as repository interfaces; Prisma isolated in the infrastructure layer.
• Composition through factories, with explicit dependency injection.
• PostgreSQL for persistence and Docker Compose for the local environment.
• Passwords with Argon2 + server-side pepper; JWT signed with an environment-provided secret, validated with Zod at boot.
• Global error handling: unexpected errors never leak stack traces to the client.

Implementation

The API’s conceptual flow:

HTTP → Routes / Controllers → Application / Use Cases → Domain → Repository abstraction → Prisma adapter → PostgreSQL.

Entities guard invariants such as name, CPF check digits, phone, and birth date. Infrastructure implements the contracts defined by the inner layers, while the domain stays unaware of framework or database details.

Quality

47 automated tests — 36 unit and 11 integration — covering the domain, use cases, adapters, HTTP, and a real PostgreSQL database in the integration tests.

CI runs, in order:

typecheck → lint → unit tests → build → integration tests.

Security

What the project guarantees today:

• Password hashing with Argon2 + server-side pepper; hashes never returned in responses.
• JWT signed with an environment-provided secret; variables validated at boot.
• .env file kept out of Git.
• Unexpected errors answered without exposing stack traces to the client.

Trade-offs

• Modular monolith instead of microservices: a single deploy, without the distributed networking and observability cost for a problem this size.
• Repository interfaces add a thin mapping layer, but they isolate Prisma and keep use cases testable without a database.
• Stateless JWT keeps infrastructure simple, but there is no revocation or refresh.
• Invariants validated in the domain; HTTP endpoints do not have dedicated Zod schemas yet.

Limitations

Stated directly, as architectural awareness: login issues a JWT, but no route validates that token yet — so no route is described here as protected. There is also no RBAC, no refresh-token rotation, no pagination, no rate limiting, and no structured observability. These are natural next steps, not hidden debt.