Overview
Backend documentation — architecture, NestJS platform patterns, events, resilience, and tooling.
This section describes how we structure Leadline backend services: architectural boundaries, NestJS dependency injection and tenancy concerns, event-centric data flows, resilience at integration edges, and extension points used by shared libraries.
For product-facing LAD material, see Leadline Architecture Design. For cross-cutting security and operations topics, see Security and Observability.
Topics
Principles
Separation of concerns, dependency direction, consistency, tenancy, and operational expectations.
Architecture
Layered APIs, hexagonal ports and adapters, and tactical DDD building blocks.
Dependency injection
Tokens, scopes, DI sub-trees, durable contexts, and multi-tenant isolation strategies.
Event-driven patterns
EDA, CQRS, event sourcing, sagas, and eventual consistency.
Reliability and concurrency
Circuit breakers and worker threads for integration and CPU-bound work.
Extensibility and tooling
IoC discovery, configurable modules, mixins, schematics, and CLI scaffolding.
Debugging
Common NestJS resolution, token, circular dependency, and scope issues.
API overview
Example layout for HTTP routes and contracts.