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01 Production-ready 2024

eMAG Marketplace Automation

A SaaS hub for eMAG sellers — orders, AWB, automated pricing and fraud detection.

E-commerceMarketplaceMulti-tenant SaaS

Context

Marketplace sellers manage orders, AWBs, prices and returns by hand across several sources. They needed a single multi-tenant hub that automates the order-to-delivery flow and keeps pricing competitive without manual work.

What I built

  • Order sync and automatic AWB generation through a courier integration (Sameday).
  • Configurable Auto-Price engine, campaign proposals, and per-order P&L.
  • IDOR-safe RBAC with recursive BFS hierarchy traversal and EF Core global query filters for tenant isolation.

Technical highlights

4-layer fraud detection

network + browser fingerprint (9 fields) + MaxMind GeoIP2 (VPN/Tor/proxy) + behavioral timing.

Custom rate limiter

dual SemaphoreSlim buckets as a Polly DelegatingHandler, to respect the external API limits without stalling the flow.

Lenient JSON contracts

tolerant converters for an external API with inconsistent responses — zero crashes on unexpected payloads.

CQRS

commands and queries separated for a domain with complex business rules.

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