dabydat/alpha-omega/nestjs-constants

NestJS Constants Strategy

Constants are the connective tissue of a microservices architecture. They provide single sources of truth for routes, message patterns, injection tokens, and topic names. Without consistent constants, services become tightly coupled and difficult to maintain.

Why Constants Matter

See references/why-constants.md for the ❌ BAD hardcoded-strings example and the ✅ GOOD constants example.

Types of Constants

1. Module Tokens (Dependency Injection) + Module Module Tokens

See references/di-tokens.md for Symbol-based tokens, module wiring, injection, and module tokens.

2. Controller Maps (Route + Message Pattern)

See references/controller-map.md for name, tag, routes, message patterns, the combined map, and the ControllerAction<T> type.

3. Client Constants (BFF Service References)

See references/client-constants.md.

4. Topic Constants + Kafka Group Constants

See references/topic-constants.md.

File Structure & Naming Conventions

See references/file-structure.md for the domain/constants/ vs infrastructure/constants/ split and the naming convention table.

Usage in Controllers

See references/usage.md for TCP (@MessagePattern) and REST BFF (route + client.send) usage.

Anti-Patterns to Avoid

See references/anti-patterns.md for the five ❌ examples (string literals, no barrel export, no layer separation, mutable constants, inconsistent naming).

Summary

Golden rule: Every string that has meaning across services should be a constant. Hardcoded strings are technical debt.