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Co-Founder & Chief Technology Officer (CTO) | Wallety | 2009

//Context & Scale

Wallety was an early payment gateway platform built to process high-concurrency online transactions in Egypt. Regional banking APIs suffered from frequent network drops, high timeout rates, and unreliable callback notifications under unstable national telecommunications infrastructure. Airlines and travel merchants required a fault-tolerant intermediary payment gateway that could guarantee transactional consistency without losing booking state or double-booking passenger seats. The platform scaled to handle 33% of all domestic air travel ticketing volume across Egypt, integrating directly with regional banking gateways and the Amadeus Global Distribution System (GDS).

//Architectural Decisions

  • ->Deterministic Transaction State Machine: Implemented an explicit transactional state engine (Pending, Authorized, Settled, Failed, Reconciled) backed by automated polling routines to reconcile dropped bank callbacks deterministically.
  • ->Master-Slave Database Topology: Dedicated the MySQL master database strictly to ACID-compliant transactional writes while routing read-heavy audit and reporting queries to read replicas, preventing disk I/O contention during peak sales.
  • ->Asynchronous Worker Pipelines: Decoupled synchronous user-facing HTTP request cycles from slow upstream banking gateways by dispatching payment settlements to persistent CLI queue daemons operating on 1-second loops.
  • ->Atomic GDS Booking Alignment: Designed transactional handshakes that coupled temporary seat holds in Amadeus GDS directly with payment pre-authorization confirmations, preventing race conditions and double bookings.

//Engineering Execution

  • ->Symfony Domain Layer: Enforced clean separation of concerns in Symfony/PHP, isolating payment state logic, banking protocol drivers, and GDS interfaces into modular service boundaries.
  • ->AWS Infrastructure & Load Balancing: Provisioned AWS EC2 compute instances behind Elastic Load Balancers (ELB) with SSL termination and automated health monitoring.
  • ->Continuous Reconciliation Daemons: Built background CLI daemons that periodically audited pending payment states against bank transaction logs, resolving unacknowledged settlements without manual staff intervention.

//Measurable Impact

  • ->33% National Flight Volume: Successfully handled high-concurrency payment throughput for one-third of Egypt's domestic airline ticketing volume.
  • ->Zero Inconsistent States: Deterministic transaction state machine and background reconcilers eliminated dropped orders and double-booking errors during external banking outages.
  • ->High-Availability Checkout: 1-second queue cycles insulated frontend checkout flows from external bank response latency, maintaining fast user response times during high-volume fare promotions.