Inventory Management Service API

Overview

The Inventory Management Service is a robust backend system designed to manage products, warehouses, stock levels, and inventory transactions at scale. Built with NestJS and TypeScript, it adopts a clean modular structure, multi-tenant data isolation, and an event-driven architecture to ensure consistency, extensibility, and reliability across inventory operations.

This service is designed as a core backend component for enterprise or SaaS platforms that require accurate stock tracking across multiple tenants and warehouses.

Key Features

• Full product lifecycle management (CRUD with soft deletes)
• Warehouse management with status tracking and soft deletion
• Inventory tracking with stock levels, minimum thresholds, and capacity limits
• Inbound and outbound stock transaction recording
• Event-driven inventory updates using NestJS event emitter
• Multi-tenant architecture with strict tenant data isolation
• Pagination, filtering, and sorting across all major resources
• Auto-generated Swagger (OpenAPI) documentation
• Dockerized local development setup

Tech Stack

Language & Runtime: TypeScript, Node.js Framework: NestJS Database & ORM: PostgreSQL, Prisma Architecture: Modular monolith, event-driven design Multi-Tenancy: nestjs-cls with Prisma client extensions Tooling: Docker, Docker Compose, Swagger, ESLint

Architecture & Design

The service follows a modular NestJS architecture, separating concerns across products, warehouses, inventory, and transactions. Multi-tenancy is enforced at the database layer using request-scoped context (nestjs-cls) combined with Prisma client extensions, ensuring complete tenant isolation without duplicating schemas.

An event-driven approach is used for inventory workflows, allowing stock updates and related side effects to be handled asynchronously and cleanly decoupled from core business logic.

My Contributions

• Designed and implemented the complete service architecture using NestJS
• Built a multi-tenant data access layer with Prisma and CLS-based context
• Implemented event-driven stock and inventory transaction handling
• Designed RESTful APIs with pagination, filtering, and sorting
• Integrated Swagger for comprehensive API documentation
• Containerized the database setup using Docker Compose

Results / Impact

• Ensured strict tenant data isolation suitable for SaaS use cases
• Enabled accurate, auditable inventory tracking across warehouses
• Improved maintainability through modular and event-driven design
• Provided clear, self-documented APIs for easy client integration

Testing & Quality Assurance

• Centralized validation using DTOs and class validators
• Defensive checks for stock availability and capacity limits
• Consistent error handling with meaningful HTTP responses
• Schema-driven database migrations via Prisma

Security Considerations

• Tenant isolation enforced via required x-tenant-id header
• Soft deletes to preserve historical data integrity
• Validation and sanitation of all incoming API requests
• Clear separation of public and protected operations

What I Learned

• Designing scalable multi-tenant backend systems
• Applying event-driven patterns in NestJS applications
• Structuring Prisma for complex relational domains
• Building maintainable APIs with strong domain boundaries