Backend Implementation Strategy¶

Purpose¶

The Backend Implementation Strategy defines how future backend work should turn Algosure architecture into a Spring Boot Modulith implementation.

Strategy¶

Principle	Implementation Direction
Modulith first	Build one Spring Boot backend with explicit application modules.
DDD aligned	Modules mirror Domains and own their source facts.
API contract aligned	Controllers implement approved API specifications only.
Database ownership	PostgreSQL tables and Liquibase migrations belong to owning modules.
Event coordinated	Cross-module workflows use internal events where appropriate.
Secure by default	Spring Security validates Keycloak tokens before business work.
Multi-tenant by default	Tenant and OrganizationId context are mandatory for customer data.
Future extraction ready	Dependencies, persistence, events, and APIs support later microservice extraction.

Dependency Direction¶

flowchart TB
    Api[api]
    Application[application]
    Domain[domain]
    Infrastructure[infrastructure]
    External[External Providers]

    Api --> Application
    Application --> Domain
    Infrastructure --> Application
    Infrastructure --> Domain
    Infrastructure --> External

Implementation Rules¶

The domain layer must not depend on API, persistence, messaging, or provider implementation details.
Application services coordinate transactions, authorization context, repositories, events, and external ports.
Infrastructure implements persistence, messaging, integration, and provider adapters.
Controllers translate HTTP contracts into commands and queries.
Shared kernel remains minimal and must not become a generic utility or business dumping ground.

Delivery Sequencing¶

Define module boundary and package structure.
Define commands, queries, DTOs, and application services.
Define domain model and policies.
Define persistence ownership and migrations.
Define internal events and outbox requirements.
Add security, validation, exception, and test coverage.