Backend
Services built for regulated domains, real traffic, and on-call support.
open to opportunities
Mohamed Hosny
Senior Software Engineer / Software Architect
Cairo, Egypt · UTC+2 · remote
I turn messy enterprise systems into reliable products fast. From national infrastructure and regulated fintech platforms to AI-native builds, I design systems that survive real production pressure.
- 8+ yrsin production
- 6industries
- 40×calibration throughput
- IEEEpublished research
Capabilities
What I Build With
Frontend
Interfaces that stay maintainable after the third team touches them.
AI
Agentic systems, orchestration, and LLM architecture that survives a budget review.
Cloud / DevOps
Infrastructure and delivery flows that keep teams shipping under pressure.
Case studies
Things I built, and what happened
5 of 11. Each one links to the full write-up with the decisions, trade-offs, and a working demo.
Betting Wallet Redesign
A wallet service where two bets placed at the same instant could both spend the same balance.
Row lockcheck and debit in one transaction
Problem
Under load, concurrent bets on one account raced each other.
What I built
Moved the check and the debit inside a single transaction that takes a lock on the wallet row before reading it.
What it cost
Writes to a single wallet now serialize, so a hot account is a throughput ceiling no number of instances can raise.
- Bet Request
- Wallet Lock
- Check & Debit
- Commit
- Settlement
Betting Wallet Redesign — request path
Computer-Use Agent
Agents that read the screen as pixels and drive legacy desktop software that offers no API to call.
< 2sscreenshot → action
Problem
Businesses need to automate complex desktop workflows — filling forms, navigating legacy software, extracting data from screens — but traditional RPA is brittle and breaks when UIs change.
What I built
Built a production platform on Claude Computer Use API with a Python/FastAPI backend.
What it cost
Vision-driven control is slower and costlier per step than scripted RPA, and it is non-deterministic — every action needs a verification read-back before the next one is safe.
- Screen Capture
- Vision Analysis
- Action Planning
- Execution Engine
- State Recovery
Computer-Use Agent — request path
Enterprise Payment Microservices2023–now
Payment services split along the boundaries that matter — gateway, payments, ledger, notifications — carrying millions of records a day.
MillionsRecords / Day
Problem
High-volume payment traffic needed dependable services and fast production fixes — millions of records a day flowing through gateway, payments, ledger, and notification paths, where downtime or backlog has direct financial impact.
What I built
Delivered .NET Core microservices with clear service boundaries, Redis-backed hot paths, and Docker-based deployment, plus the hotfixes and operational support that keep a high-throughput payments platform healthy under real load.
What it cost
Clear service boundaries cost cross-service consistency — transactions stay inside a single service and the ledger reconciles afterwards.
- API Gateway
- Payments Service
- Ledger Service
- Notifications
Enterprise Payment Microservices — request path
Smart Meter Calibration System2018
A multithreaded calibration pipeline that took smart-meter manufacturing from one meter per cycle to forty.
40×1 → 40 meters per cycle
Problem
Manufacturing throughput was capped by a slow, sequential calibration workflow — each meter processed one after another, leaving expensive production lines waiting.
What I built
Re-architected calibration around a multithreaded, batch-oriented pipeline tuned to the production hardware.
What it cost
Parallelising the line meant giving up a simple failure model: one meter faulting mid-grid must not take the other thirty-nine with it, so per-slot error isolation and recovery became the real work.
- Batch Intake
- Parallel Calibration
- Result Streaming
- Verification
Smart Meter Calibration System — request path
Healthcare EDI & HL7 Integrations2022
Dynamic 835/837 EDI and HL7 parsers that turn messy, multi-vendor healthcare interchange into reliable structured data.
835/837EDI Formats Parsed
Problem
Clinical and billing systems exchange data as dense X12 EDI (835 remittance, 837 claims) and HL7 messages that vary by vendor and break rigid parsers.
What I built
Built schema-driven parsers that tokenize the X12 stream, resolve segment definitions dynamically, validate loops and control numbers, and normalize everything into internal claim and remittance models — then route the results through Iguana, a fax gateway, or internal services.
What it cost
A schema-driven parser is slower and harder to debug than a hand-written one per vendor, and it adds a schema registry to maintain.
- Segment Tokenization
- Schema Resolution
- Validation
- Transformation
- Routing
Healthcare EDI & HL7 Integrations — request path
System design
Three shapes I draw a lot
Whiteboard defaults I reach for before reaching for anything clever.
The boring one that pays the bills
Most business software is this shape. The work is in the boundaries, not the boxes.
- Userbrowser
- APIREST
- Backendservices
- DatabasePostgres
Retrieval before generation
An agent is only as good as the context it is handed. Retrieval is the product; the model is a dependency.
- Appchat / task
- AI Agenttool use
- RAGvector store
- LLMvLLM / API
Real-time without the pain
Sockets are easy until you run two instances. Shared state is what makes it survive a deploy.
- ClientWebSocket
- Gatewaysticky-free
- Backendhandlers
- Redispub/sub
Experience
Where the scar tissue came from
Government infrastructure, Saudi fintech regulation, healthcare interoperability, payments, manufacturing, and AI — in that order.
Senior Software Developer
Enterprise payments platform · remoteMar 2023 – Present- Microservices enterprise payment solution — .NET Core, Azure, SQL Server
- Optimized large-scale data processing handling millions of payment records
Senior Full-Stack Developer
Healthcare & payments consultancy · remoteJan 2022 – Mar 2023- Built modular ISO 8583 solutions with dynamic 835/837 EDI healthcare parsing
- Integrated Fax, HL7 via Iguana, and internal healthcare systems
Full-Stack Session Lead
Engineering education · remoteApr 2021 – Aug 2021 · alongside the day job- Mentored 50+ full-stack nanodegree students in Node.js, Express, React
- Weekly meetups, code reviews, and one-on-one sessions guiding certification
Senior Software Developer
Healthcare & fintech consultancy · remoteApr 2020 – Jan 2022- Full-stack healthcare & fintech platforms — .NET Core, Node.js, Angular, AWS
- Secure OAuth2.0 authentication with IdentityServer for multi-tenant apps
Senior Software Developer
Smart-meter manufacturing · on-siteMay 2017 – Apr 2020- Calibration system that took the line from one meter per cycle to forty
- Low-level DLMS & IEC 1107 protocols for smart meter manufacturing
Software Developer
Enterprise GIS · on-siteOct 2016 – May 2017- WPF/MVVM applications with DevExpress for enterprise GIS-integrated solutions
- Legacy system modernization and improved GIS data processing responsiveness