SupplyLens

An inventory & supply-chain risk analytics API. Given historical demand for a set of SKUs across multiple sites — plus lead time, ordering cost, holding cost, and a target service level — SupplyLens calculates, for each SKU/site combination:

• Economic Order Quantity (EOQ) — the order size that minimises total ordering + holding cost
• Safety Stock — buffer stock to cover demand variability during lead time, at a chosen service level
• Reorder Point (ROP) — the stock level that should trigger a new order
• Stockout risk flag — 🔴 / 🟠 / 🟢 per SKU/site, comparing current on-hand stock to the ROP

It surfaces which sites and SKUs are at risk of running out, and what to order — the kind of operations-research logic used in warehousing and mine-site inventory planning.

🔗 Live demo: coming soon 📂 Frontend: a /projects/supplylens page in my portfolio site (coming soon)

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Architecture

A single solution split into three projects, so business logic never lives in a web controller:

flowchart LR
    FE[Frontend<br/>Next.js page] -- HTTP/JSON --> API
    subgraph Backend [Backend solution]
        API[SupplyLens.Api<br/>controllers · DTOs · auth · Swagger]
        CORE[SupplyLens.Core<br/>EOQ / safety-stock / ROP logic · models]
        INFRA[SupplyLens.Infrastructure<br/>EF Core · PostgreSQL]
        API --> CORE
        API --> INFRA
        INFRA --> CORE
    end
    INFRA -- SQL --> DB[(PostgreSQL)]

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• SupplyLens.Core — domain models and the EOQ / safety-stock / ROP calculations. Pure C#, depends on nothing. This is where the business logic lives.
• SupplyLens.Infrastructure — data access: EF Core DbContext, migrations, PostgreSQL.
• SupplyLens.Api — the web layer: HTTP endpoints, request validation, JWT auth, Swagger docs.
• SupplyLens.Core.Tests — xUnit tests for the calculation logic.

Dependencies point one way (Api → Core ← Infrastructure): the math has no knowledge of the web or the database, which keeps it isolated, testable, and reusable.

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Tech stack

Layer	Technology
Language / runtime	C# · .NET 10
Web framework	ASP.NET Core (controllers)
Data access	EF Core · Npgsql
Database	PostgreSQL (Azure Database for PostgreSQL)
Auth	JWT · BCrypt password hashing
API docs	Swagger / OpenAPI
Tests	xUnit
Hosting	Azure App Service (planned)

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Running locally

Prerequisites: .NET SDK 10 and a PostgreSQL database (this project uses Azure Database for PostgreSQL; any Postgres works — local, Docker, or hosted).

# from the repository root
dotnet build                              # build all projects
dotnet test                               # run the unit tests
dotnet run --project SupplyLens.Api       # start the API

The API prints the URL it's listening on (e.g. http://localhost:5xxx). Open /swagger on that URL for interactive API documentation.

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Key formulas

Metric	Formula
EOQ	sqrt( (2 × annualDemand × orderingCost) / holdingCostPerUnit )
Safety Stock	zScore × stdDevOfDemandDuringLeadTime
Reorder Point	(averageDailyDemand × leadTimeDays) + safetyStock

The service-level z-score uses a lookup table for common confidence levels (90% → 1.28, 95% → 1.645, 99% → 2.33).

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Status

🚧 Work in progress — built as a focused portfolio project to demonstrate production-quality C# / ASP.NET Core. See commit history for progress.