Listening: Codebase Introduction Call

Monorepo (mono repository) = a single repository that holds multiple projects, services, or packages. The opposite is a polyrepo (each service in its own repository).

Common monorepo patterns in IT:

• API + frontend + shared libraries in one repo (as in this example)
• Workspaces managed by tools like Nx, Turborepo, Lerna, or Bazel

Advantages: Atomic cross-service changes, shared tooling, single source of truth for dependencies.

Challenges: Larger clone size, more complex CI, stricter access controls needed.

"Don't worry about X for now" — a very common onboarding phrase that signals the speaker is deliberately narrowing scope. It is not dismissive — it is helping the new hire focus without being overwhelmed.

Repository layer (in the Repository Pattern) = the layer responsible for data access. It abstracts database operations from the rest of the application — the service layer calls repository methods, not raw SQL or ORM calls directly.

Layered architecture vocabulary:

• Handler / Controller layer — receives HTTP requests, validates input, calls service layer
• Service layer — contains business logic; orchestrates operations
• Repository layer — talks to the database; abstracts data access

"Don't touch X until you're comfortable with Y" — a classic onboarding instruction pattern. It defines a learning order and protects sensitive or complex code from being accidentally modified by someone still learning the system.

End-to-end (e2e) tests simulate a complete user flow through the entire application stack — from the frontend UI or API entry point through business logic, down to the database, and back.

Why e2e tests are slow:

• They require a running application with all dependencies (DB, external services)
• They often use browser automation (Playwright, Cypress) which adds overhead
• A single e2e test can take seconds to minutes vs milliseconds for unit tests

Testing vocabulary summary:

• Unit test — tests a single function or class in isolation; very fast
• Integration test — tests interactions between components (e.g., service + database)
• e2e test — tests the full application flow; slow but high confidence

"Don't be discouraged if you break something early" — a supportive onboarding register phrase. It normalises mistakes for new hires and signals that the team has safety nets (PRs, code review) to catch them.