Mohammad Kabalan

Senior software engineer with 9+ years building and scaling web applications across the full stack. Strong backend and distributed-systems focus: multi-tenant SaaS, API design, database-level security, and async/event-driven architecture, paired with frontend delivery in React/Next.js. A daily Claude user across the full development lifecycle turning requirements into designs, pair-programming production features, debugging, and accelerating code review and refactoring.

Experienced leading development efforts and owning mission-critical, high-availability platforms in production.

Senior Full-Stack Developer at Propwise Real Estate (2026-02 – 2026-07)

• Engineered database-level tenant isolation for a multi-tenant SaaS platform using PostgreSQL Row-Level Security, preventing cross-tenant data leaks even when application-layer filters are missing — eliminating an entire class of correctness bugs.
• Replaced a slow multi-table ILIKE search with a denormalized search index and async indexer pipeline, cutting median query latency from ~800 ms to under 100 ms; added full-text/trigram query routing over GIN indexes and Arabic/mixed-script normalization for a bilingual user base.
• Built a tamper-proof audit-logging system using PostgreSQL triggers across 35 tables, capturing every insert/update/delete with before/after values, user, session, and IP enforced at the database level so it cannot be bypassed by application code or raw SQL.
• Designed a two-layer RBAC system (endpoint guards + per-record permission flags) with a 5-minute permission cache, cutting per-request authorization lookups by ~70% while keeping role changes near-instant via cache invalidation.
• Built a multi-portal real estate syndication system (Property Finder, Bayut, dubizzle): REST push with async webhook confirmation, public XML feeds, credit gating, and a 9-state sync state machine, plus automated inbound lead capture from portal webhooks and polling APIs into the CRM pipeline.
• Built an automated lead-distribution and escalation system: priority-ordered rules with workload balancing and skill matching, plus a tiered state machine (notify, re-tag, redistribute) that detects stale leads — all running async via a job queue so assignment never blocks lead intake.
• Built the platform's async-work foundation on a Postgres-native job queue (pg-boss, no Redis/RabbitMQ): worker concurrency, deduplication, retries with backoff, and reconciliation sweepers ensuring no background job is silently dropped.

Senior Software Engineer at Siemens Industrial L.L.C (2023-11 – 2026-01)

Owned end-to-end development and production support of the 999 emergency-response platform — a high-availability system where downtime directly impacts public safety and emergency response times.

• Re-architected the incident distribution and escalation engine, replacing legacy routing logic with a rule-driven pipeline that dispatches incidents to the correct response units and automatically escalates unacknowledged or overdue cases — reducing missed-SLA incidents and manual dispatcher intervention.
• Designed and delivered real-time operator dashboards streaming live incident state, unit availability, and SLA alerts, enabling dispatchers to make faster, better-informed decisions under pressure.
• Built a real-time log-monitoring dashboard that parsed user-level log files to detect critical errors and exceptions, surfacing live alerts and insights for faster issue resolution.
• Integrated the platform with third-party APIs and government data sources, enabling secure, seamless data exchange; authored automation scripts (log rotation, health checks, scheduled jobs) that reduced manual operations workload.
• Collaborated with system architects and product managers on roadmap features and defect triage, translating control-room requirements into technical designs; built and productionized end-to-end automated testing for the platform.

Senior Full-Stack Developer at SpaceToonGo L.L.C (2021-09 – 2023-09)

• Contributed to re-architecting the platform backend from a PHP monolith to a GraphQL Federation microservices architecture (v5): Apollo Gateway composing 12+ NestJS/TypeScript subgraphs in an Nx monorepo, each owning its own database (Postgres/Prisma, MongoDB) — with JWT verification and identity injection at the gateway.
• Integrated ~10 MENA payment providers (cards, cash codes, carrier billing, and Google/Apple/Huawei IAP with server-side receipt verification), secured by IP-allowlisted, HMAC-verified webhooks and async reconciliation jobs.
• Secured payment webhooks with defense-in-depth (IP allowlisting + SHA-512 HMAC signature verification) and built background reconciliation jobs to re-verify pending transactions, with async subscription updates via Google Pub/Sub.
• Scaled the read-heavy catalog API by serving the hottest endpoints (series details, episode lists) as pre-rendered static JSON — bypassing framework and database entirely — keeping the platform stable under traffic spikes; reduced load times by 50%, contributing to a 10% increase in subscription revenue.
• Implemented secure video delivery: per-request signed, expiring CDN URLs (Limelight/Edgio, CDN77, Wowza) with user-traceable tokens, so leaked stream links auto-expire and can be traced back to the account.
• Designed a sharded, denormalized entitlement cache so subscription checks on every video play avoid hitting the main subscription database — plus geo-gated content, pricing, and payment-method selection per country (MENA/GCC) via Cloudflare edge headers.

Full-Stack Developer at SDNone (2020-09 – 2021-08)

Led the team building Elite Auction — a bilingual (Arabic/English) e-commerce and live-auction marketplace serving four surfaces from a single Laravel codebase: customer storefront, admin dashboard, vendor dashboard, and a mobile API.

• Designed a multi-guard architecture (customer/admin/vendor session guards + JWT API guard), allowing four independent applications to share one codebase and data model.
• Built the live auction engine: timed auctions, bid validation against the current highest bid, pseudonymous bidder handles for privacy, and a real-time polled leaderboard.
• Delivered a multi-vendor marketplace with admin-provisioned vendor accounts, shop-approval workflows, and vendor self-service product management; built and documented a 30+ endpoint mobile REST API secured with JWT, with per-request AR/EN language switching.
• Led sprint planning, code reviews, and technical mentoring, setting review standards that reduced defect rates in downstream releases.

Backend Engineer at Norrdex Travel Agency (2017-01 – 2020-08)

Built and maintained the production travel-agency platform (Laravel/PHP, MySQL): flight-ticket inquiries, visa application requests, travel offers, event bookings, and a newsletter system — moving the agency's bookings from phone/walk-in to online, with every inquiry stored and auto-emailed to staff.

• Built a complete custom admin panel for offers, visa products, bookings, customer messages, and dynamic site settings — enabling non-technical staff to manage the site without a developer.
• Designed, documented, and versioned internal REST APIs, reducing integration friction for downstream services and third-party partners.
• Handled production operations single-handedly: hosting configuration, production database provisioning, DNS/domain and company email management, SMTP transactional email integration, and on-call incident support.

BSc in Software Engineering – YPU University (2014)