Mid-level software engineer · open to roles Cairo, GMT+2
I build .NET software that real businesses run on.
I'm Sayed Elmahdy, a mid-level software engineer with 2.5 years of shipping complete systems in ASP.NET Core: Web APIs, MVC applications, dashboards and integrations. Right now my multi-tenant platform serves three live storefronts from one codebase.
Engineering
Production access
Production access
On call · Cairo
- 0
- systems shipped to real users
- 0
- live stores on one multi-tenant platform
- 0
- automated tests on the platform
- 0
- payment gateways behind one adapter
In production
One engine.
Three brands.
All live.
At Z4U I work on a multi-tenant ERP and e-commerce platform. Each tenant gets its own brand, database, domain and configuration. Underneath, it's the same ASP.NET Core API, deployed as Docker containers on a Linux VPS.
Anatomy of an order
What happens after a customer taps Checkout, from the edge to the ERP. Every stage below is code I wrote or configured.
- StorefrontThree branded tenants in Arabic and English.
- Cloudflare edgeWAF, DDoS protection, bot rules and CDN caching in front of every site.
- Reverse proxyTLS termination and routing to each tenant's container.
- ASP.NET Core 8 APIRate limiting, JWT and permission policies, tenant resolution, validation, then the order service.
- SQL Server + RedisStock, order and journal entry committed in one transaction. Hot catalog data cached.
- Outbox + HangfireEvents saved with the order, then dispatched by workers with retries and a 15-minute reconciliation sweep.
- PartnersPayment gateways, shipping carriers, notifications and ERP sync behind adapters.
Under the hood
- 01Payments without plaintext secrets
- 18 payment gateways (Paymob, Tabby, MyFatoorah, PayPal, Stripe and more) behind one provider store. Credentials are sealed with a per-tenant Data Protection key ring.
- 02Pluggable shipping
- Dynamic shipping providers (Aramex, SMSA and others), weight-based rates, map-first delivery addresses and printable labels.
- 03ERP ↔ store sync
- Items, stock and prices flow from the ERP to the storefront through an outbox worker, so every sale and return updates inventory and accounting.
- 04Built for the region
- Multi-currency pricing, country-level payment policies and bilingual Arabic and English API responses.
- 05Self-healing jobs
- Hangfire runs invoices, notifications and a reconciliation sweep every 15 minutes that catches payments whose callback never arrived.
- 06Real operations
- Split and delayed orders, admin order amendments, trader accounts, promotions and coupons, and approval workflows with activity reports.
- 07Tested like it matters
- Around 1,900 automated xUnit tests, from money and refund math to integration tests running the real API in memory. k6 load tests model a real homepage visit.
- 08Shipped by pipeline
- GitHub Actions builds the image and redeploys each tenant's containers. Serilog and Seq for logs, health checks on the key ring and dependencies.
Selected work
Systems I designed
and shipped end to end.
ERP + E-Commerce Backend Platform
A single .NET 8 API that is the source of truth for catalog, inventory and finance, and also runs the online store.
- Procurement, stock movements, sales bills and journal entries, all connected to checkout, orders and shipments.
- JWT auth with fine-grained permission policies across accounting, catalog, cart, orders, shipping and analytics.
- Hangfire jobs for invoices and notifications. Invoices and shipping labels are generated as PDFs.
Architecture & features
Source private
Facebook Messenger Campaign API
Lets a business connect its Facebook Pages and send personalised, scheduled Messenger campaigns while watching replies arrive live.
- OAuth page connect with long-lived tokens and automatic webhook subscription.
- Time-zone aware scheduling, placeholders, image uploads converted to WebP, and progress tracking.
- Incoming messages via webhooks, pushed to the dashboard in real time over SignalR. Rate limits with retry and backoff.
Project docs
Source private
Conscript Affairs Management System
Built during my military service: a central ASP.NET Core MVC system that replaced paper and spreadsheets for attendance, leave and daily reporting.
- Role-based access control and audit logging for sensitive operational data.
- Dashboards by department, officer and status, with scheduled backups and exports.
- Background jobs and real-time updates that cut manual administrative work. Recognised with an official certificate.
Redacted docs & certificate
Classified source
More projects
- 2026 Cairo Airport Staff Management Arabic-first attendance, shifts and leave system with 2FA, audit logs, Excel import and PDF reports. MVC 8 · EF Core · xUnit Private
- 2026 Elmahdy Relay Production-grade ESP8266 smart relay firmware: MQTT, Home Assistant, installable PWA, OTA updates. C++ · IoT · MQTT
- 2026 WhatsApp REST API Multi-tenant WhatsApp service: session lifecycle, OTP, webhooks, WebSocket events, Prometheus metrics. Node · Docker · Redis Private
- 2025 Tailor ERP ERP for tailoring and garment businesses, bilingual, with real-time updates and background jobs. MVC 8 · Dapper · SignalR Private
- 2026 GameFix Doctor Pro Windows diagnostics tool for gamers: health scans, safe repairs, snapshots and rollback. Python · Windows
- 2026 Dental Reports System Team project: N-tier dental clinic reporting system. I contributed to the codebase. MVC · N-tier Private
- 2024 Electronic Mind of Alzheimer Patient Graduation project. Care backend with SignalR live updates and face recognition to help patients recognise family. Web API · FastAPI · OpenCV
Inside the systems
Real screens from
software I shipped.
Captured from the running applications. Personal data is blurred or replaced with demo data.
Experience
I kept shipping,
even in uniform.
During a full year of military service I built the Ministry system by day and kept Z4U's production systems running remotely.
a7f3e21HEAD → mainFeb 2026 · nowRejoined Z4U full-time as .NET Developer
Backend architecture, payment and shipping integrations, and performance work on a multi-tenant platform that runs three live stores.
5d0c9b4merge serviceFeb 2026Completed military service
Delivered the Conscript Affairs system and kept Z4U production running at the same time.
e19b7a2serviceFeb 2025 · Feb 2026ASP.NET MVC Developer, government entity
Attendance, leave, reporting and dashboards with RBAC and audit logging. Recognised with an official certificate.
3c44f10Feb 2025 · Feb 2026Part-time at Z4U, remote
API enhancements, bug fixes and database optimisation so the stores never stopped moving.
8b2d6e5Apr 2024 · Jan 2025Joined Z4U as .NET Developer
ERP, e-commerce and SaaS features, REST APIs, payment and shipping integrations, query tuning and caching.
0f9a13cv1.02024B.Sc. Computer Science, El Shorouk Academy
GPA 3.5 / 4.0. Graduation project: Electronic Mind of Alzheimer Patient.
c0ffee12021 · 2023Mentor at GDSC and CPC
Taught programming languages and problem solving to fellow students.
Stack
C# at the core.
Full systems around it.
Used in production
Familiar
.NET
The core of everything I ship
- C#
- ASP.NET Core 6 to 10
- Web API
- MVC
- Razor
- Minimal APIs
- Middleware & DI
- Background services
- AR / EN localization
Data
Modelled, tuned and migrated in production
- SQL Server
- EF Core
- Dapper
- Redis
- Query tuning
- Indexing
- Stored procedures
- Bulk operations
- MySQL
Architecture
How the platform stays maintainable
- Clean Architecture
- Multi-tenancy
- Outbox pattern
- Domain events
- SOLID
- Repository & Unit of Work
- Microservices
Payments & shipping
Real money and real parcels
- Paymob
- Tabby
- MyFatoorah
- PayPal
- Tap
- Kashier
- PayTabs
- Moyasar
- Checkout.com
- Aramex SOAP / WCF
- SMSA
Integrations
Talking to the outside world
- Facebook Graph API
- Google OAuth
- Cloudinary
- Resend
- Webhooks
- REST & SOAP clients
- OpenAPI
Realtime & jobs
Work that happens without a click
- SignalR
- Hangfire
- WebSockets
- Recurring jobs
- Reconciliation sweeps
- RabbitMQ
Security
Built in, not bolted on
- JWT
- OAuth 2.0
- ASP.NET Identity
- RBAC & policies
- 2FA
- Data Protection
- Audit logs
- OWASP Top 10
Testing
Proof that it works
- xUnit
- WebApplicationFactory
- Integration tests
- Postman suites
- k6 load tests
DevOps
From commit to live
- Docker
- GitHub Actions
- Linux VPS
- Nginx
- Cloudflare
- Serilog + Seq
- Health checks
- Azure
Documents
Invoices, labels and imports
- QuestPDF
- EPPlus
- ImageSharp
- QR & barcodes
Frontend
Enough to ship the whole feature
- Razor views
- JavaScript
- jQuery
- Bootstrap
- Chart.js
- RTL layouts
- PWA
- React
- Next.js
Beyond .NET
Right tool for the job
- Python
- FastAPI
- Node.js
- C++ · ESP8266
- MQTT
- OpenCV
- Flutter