I specialize in legacy PHP/MySQL systems, Node.js backends, APIs, integrations and performance optimization — the parts of a business that have to keep running.
From slow databases and fragile legacy applications to complex third-party integrations, I help teams diagnose difficult technical problems and build reliable solutions — without unnecessary rewrites.
Senior Software Engineer
Owning a production ERP/CRM day to day
Legacy PHP / MySQL
Maintaining and modernizing business-critical systems
Backend-heavy engineering
APIs, business logic and data at the core
Performance work
Reduced a hot ERP page from 600+ queries to ~15
Cloud migration
Phased move with zero data loss, minimal downtime
Integrations
Shipping carriers, payments and accounting systems
The problem I solve
Systems get slow. Legacy code accumulates. Integrations break. And the people who understand it are stretched thin or gone. I step into existing production systems, find the real cause of the problem, and make targeted, low-risk improvements that keep the business running.
Focused engagements around production, backend and legacy systems.
Real systems, real constraints, real outcomes — not demo apps.
Large-scale enterprise operations platform for a wholesale distribution business. Handles complex inventory management, multi-currency transactions, and integrates with CRM, payment gateways, and shipping providers. Achieved 40% performance optimization on critical data pipelines.
Full-stack enterprise collaboration platform built as an Atlassian Jira Connect application. Features advanced real-time diagramming with operational transformation, project planning with bidirectional Jira synchronization, team surveys, and multi-user collaboration.
Progressive Web App connecting service professionals with clients. Built 80+ screens with intelligent discovery, complete booking management, secure Stripe payments, real-time messaging, and event ticketing. Achieved 87% onboarding completion rate and 98.4% payment success rate.
A calm, low-risk process built around production stability.
We talk through the system, the problem and the outcome you actually need — before touching any code.
I inspect the relevant code, architecture, database and infrastructure to find what is really going on.
I identify the root cause and propose the smallest practical solution, with the trade-offs made clear.
I make the changes with production stability in mind — careful, reviewable, and safe to ship.
Where it helps, I keep supporting and improving the system so it stays reliable over time.
The teams and situations where an experienced engineer makes the biggest difference.
Companies with valuable existing software that needs maintaining, stabilizing or modernizing — without throwing it all away.
Teams that need extra senior backend capacity for specific projects, integrations or a period of heavy delivery.
Businesses relying on order processing, shipping, ERP and operational systems where downtime and errors cost money.
Organizations that need someone experienced to diagnose and solve production problems without making a full-time hire.
The tools I reach for — organized by what they actually do.
Practical write-ups on production debugging, performance and legacy systems.
A field account of wiring the FedEx REST APIs into a long-lived in-house PHP platform — OAuth, live negotiated rates, paperless customs documents, per-box thermal labels — and the data discipline that actually gets a parcel through customs. No rewrite, no downtime.
A commerce team complained their estimate page was hanging for 10 seconds. Nothing in the code had changed. The culprit turned out to be a single line in the MySQL 8.0 changelog — and fixing it meant applying three layers of caching to a codebase that pre-dated modern PHP frameworks.
A detailed technical walkthrough of migrating a business-critical PHP platform from a single in-office server to managed cloud infrastructure using binary-log replication — with only ~10 minutes of user-visible downtime and zero data loss.
Whether you're dealing with a slow application, a legacy codebase, a difficult integration, or you simply need senior engineering capacity — tell me what you're working with, and I'll let you know how I can help.
Or email me directly at osamah.hafeez@gmail.com
