Microservices & Transport Standards

Priority: P0 (FOUNDATIONAL)

Microservices communication patterns and transport layer standards.

• Synchronous (RPC): Use gRPC for low-latency, internal service-to-service calls (10x faster than REST/JSON).
• Asynchronous (Events): Use RabbitMQ or Kafka for decoupling domains via fire-and-forget (emit()).

gRPC Setup

See implementation examples

RabbitMQ Setup

See implementation examples

Monorepo Contracts

• Store all DTOs, .proto files, and Interfaces in libs/contracts.
• Services never import from sibling services — only from contracts.
• Semantic versioning of messages is mandatory. Never change a field type; add a new field.

Exception Handling

Standard HttpException is lost over RPC/TCP. Use RpcException with global filters:

See implementation examples

Serialization

• Apply useGlobalPipes(new ValidationPipe({ transform: true })) in MicroserviceOptions setup, not just HTTP.

Anti-Patterns

• No cross-service imports: Services must import only from libs/contracts, never from sibling services.
• No HttpException in RPC: Use RpcException with a global RpcExceptionFilter for microservice errors.
• No unversioned message schema: Add new fields; never change existing field types — consumers will break.