Full-stack engineer building fintech, SaaS, and real-time platforms from Nairobi, Kenya.

• African payment rails — production M-Pesa Daraja 2.0 integrations (STK Push, C2B Paybill/Till, B2C disbursement, asynchronous callback reconciliation, STK query polling for unreachable-customer edge cases), Airtel Money cross-border flows across KE → UG / TZ / RW / ZM corridors, plus Pesapal, DPO Pay, and Flutterwave gateways
• Complex payment systems — end-to-end financial transaction engines with double-entry ledger accounting, idempotent transaction handling, multi-currency wallets, automated reconciliation pipelines, fraud detection rules, webhook retry queues with exponential back-off, and real-time balance consistency under concurrent writes
• Non-custodial crypto settlement — on-chain TRC-20 and BEP-20 payment verification via TronGrid and BSC public RPC. Validates recipient address, token contract, amount tolerance, block confirmation, and deposit-window timestamp to prevent TXID replay and front-running
• Multi-tenancy complex systems — fully isolated multi-tenant SaaS architectures with per-tenant database partitioning, subdomain routing, role-based access control (RBAC), tenant-scoped billing engines, usage metering, plan enforcement, and white-label customisation. Built to support hundreds of tenants on a shared infrastructure without cross-tenant data leakage
• Real-time event-driven platforms — WebSocket-backed pub/sub architectures with Redis fan-out for horizontal scaling, tick-based state machines, graceful reconnect and session recovery, event sourcing with audit trails, and queue-based background job orchestration via Laravel Horizon and BullMQ
• API design & developer experience — RESTful and event-driven API design with OpenAPI specs, versioning strategies, rate limiting, HMAC request signing, token lifecycle management, and SDK generation. Built for third-party developer consumption
• SaaS infrastructure & billing — subscription lifecycle management, seat-based and usage-based pricing models, proration, dunning workflows, invoice generation, and revenue analytics dashboards
• Telegram commerce products — subscription bots with inline-keyboard checkout, deep-link attribution, access-code lifecycle (issue → activate → expire), unified M-Pesa + Binance Pay + PayPal + crypto purchase flow inside a single /start session
• Merchant platforms & offline-first PWAs — Laravel + React + MySQL production stacks, IndexedDB-backed offline sync for intermittent-connectivity markets, WhatsApp Business API automations, informal-sector credit scoring
• Production infrastructure — Nginx reverse proxies, systemd-managed services, GitHub Actions CI / CD, hardened VPS deployments (Hostinger, DigitalOcean, Hetzner)

• Authoring the laravel-mpesa open-source package suite — modular Composer packages covering STK Push, C2B, B2C, B2B, webhooks, reconciliation, multi-tenancy, caching, rate-limiting, fraud detection, and Filament admin — designed to be the definitive M-Pesa integration layer for the Laravel ecosystem
• Building an offline-first PWA for Kenyan Jua Kali traders — inventory, M-Pesa till integration, WhatsApp order intake, informal-sector credit scoring
• Running Telegram-native subscription products with unified fiat + crypto checkout across African markets

Freelance and contract — payment integrations (M-Pesa Daraja a specialty), complex multi-tenant SaaS, Telegram commerce bots, and real-time event-driven systems. Stack: Laravel, Python, TypeScript / React, Node, MySQL.

Reach me at hi@felixmuhoro.dev or via felixmuhoro.dev.